Revisions for Oil Testing Kit
| 131 | warren |
October 07, 2014 21:44
| over 9 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. KickstarterWe're running a Kickstarter campaign to distribute a run of these kits. Watch this video to learn a bit about it, and about the Public Lab community: Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren LabelingLabel sample bottles with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context. This photo is of a sample already dissolving in mineral oil, but typically we've collected relatively dry samples and dissolved them later. You can put a small amount into an empty sample jar or use the cue tips to put residue directly into mineral oil as in the next step.
Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit. LEDs are also not as narrow wavelength as a laser.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, in this case we're causing the samples to glow by exciting them with a high-energy UV light. When we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.  
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs we've recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org, which connects to your USB webcam. The illustrations above show a couple ways we've folded up or modified boxes to keep a spectrometer lined up with a sample container and a jar. The hard parts are getting the laser lined up with the slit, so the light actually goes into the spectrometer, and using a pretty sensitive webcam so that it can actually detect the light. One thing not shown as clearly above is that you should either turn the lights off or cover the box so that you don't detect ambient light from the room.
The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software:
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. You should also use "RGB mode" (in the Tools section of a saved spectrum page) to check that none of the three channels is overexposed. We'll add an automated warning for overexposure, soon:
This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samples and compareAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Add the spectrum of your unknown sample and see which of the others it is closest to. Calibration and intensityYour spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. If your scans were not made with the same amount of light, or if the spectrometer was not aligned the same way, two scans of the same material may not appear the same on your plot -- which would make it hard or impossible to see your sample is a good match or not. Some research suggests that such spectra should be comparable if their area is equalized -- this remains to be demonstrated Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit LiteratureWe've begun to collect research papers about fluorescence spectroscopy -- and summaries, esp. for those which are not open-access -- here: http://publiclab.org/wiki/oil-testing-kit-literature Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 130 | warren |
October 07, 2014 21:39
| over 9 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. KickstarterWe're running a Kickstarter campaign to distribute a run of these kits. Watch this video to learn a bit about it, and about the Public Lab community: Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren LabelingLabel sample bottles with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context. This photo is of a sample already dissolving in mineral oil, but typically we've collected relatively dry samples and dissolved them later. You can put a small amount into an empty sample jar or use the cue tips to put residue directly into mineral oil as in the next step.
Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit. LEDs are also not as narrow wavelength as a laser.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, in this case we're causing the samples to glow by exciting them with a high-energy UV light. When we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs we've recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samples and compareAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Add the spectrum of your unknown sample and see which of the others it is closest to. Calibration and intensityYour spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. If your scans were not made with the same amount of light, or if the spectrometer was not aligned the same way, two scans of the same material may not appear the same on your plot -- which would make it hard or impossible to see your sample is a good match or not. Some research suggests that such spectra should be comparable if their area is equalized -- this remains to be demonstrated Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit LiteratureWe've begun to collect research papers about fluorescence spectroscopy -- and summaries, esp. for those which are not open-access -- here: http://publiclab.org/wiki/oil-testing-kit-literature Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 129 | warren |
October 07, 2014 18:21
| over 9 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. KickstarterWe're running a Kickstarter campaign to distribute a run of these kits. Watch this video to learn a bit about it, and about the Public Lab community: Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren LabelingLabel sample bottles with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context. This photo is of a sample already dissolving in mineral oil, but typically we've collected relatively dry samples and dissolved them later. You can put a small amount into an empty sample jar or use the cue tips to put residue directly into mineral oil as in the next step.
Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit. LEDs are also not as narrow wavelength as a laser.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samples and compareAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Add the spectrum of your unknown sample and see which of the others it is closest to. Calibration and intensityYour spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. If your scans were not made with the same amount of light, or if the spectrometer was not aligned the same way, two scans of the same material may not appear the same on your plot -- which would make it hard or impossible to see your sample is a good match or not. Some research suggests that such spectra should be comparable if their area is equalized -- this remains to be demonstrated Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit LiteratureWe've begun to collect research papers about fluorescence spectroscopy -- and summaries, esp. for those which are not open-access -- here: http://publiclab.org/wiki/oil-testing-kit-literature Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 128 | warren |
October 06, 2014 23:08
| over 9 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. KickstarterWe're running a Kickstarter campaign to distribute a run of these kits. Watch this video to learn a bit about it, and about the Public Lab community: Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren LabelingLabel sample bottles with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context.
Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samples and compareAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Add the spectrum of your unknown sample and see which of the others it is closest to. Calibration and intensityYour spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. If your scans were not made with the same amount of light, or if the spectrometer was not aligned the same way, two scans of the same material may not appear the same on your plot -- which would make it hard or impossible to see your sample is a good match or not. Some research suggests that such spectra should be comparable if their area is equalized -- this remains to be demonstrated Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit LiteratureWe've begun to collect research papers about fluorescence spectroscopy -- and summaries, esp. for those which are not open-access -- here: http://publiclab.org/wiki/oil-testing-kit-literature Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 127 | warren |
September 24, 2014 13:58
| over 9 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren LabelingLabel sample bottles with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context.
Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samples and compareAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Add the spectrum of your unknown sample and see which of the others it is closest to. Calibration and intensityYour spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. If your scans were not made with the same amount of light, or if the spectrometer was not aligned the same way, two scans of the same material may not appear the same on your plot -- which would make it hard or impossible to see your sample is a good match or not. Some research suggests that such spectra should be comparable if their area is equalized -- this remains to be demonstrated Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit LiteratureWe've begun to collect research papers about fluorescence spectroscopy -- and summaries, esp. for those which are not open-access -- here: http://publiclab.org/wiki/oil-testing-kit-literature Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 126 | warren |
September 04, 2014 13:25
| over 9 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren LabelingLabel sample bottles with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context.
Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samples and compareAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Add the spectrum of your unknown sample and see which of the others it is closest to. Calibration and intensityYour spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. If your scans were not made with the same amount of light, or if the spectrometer was not aligned the same way, two scans of the same material may not appear the same on your plot -- which would make it hard or impossible to see your sample is a good match or not. Some research suggests that such spectra should be comparable if their area is equalized -- this remains to be demonstrated Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit LiteratureWe've begun to collect research papers about fluorescence spectroscopy -- and summaries, esp. for those which are not open-access -- here: http://publiclab.org/wiki/oil-testing-kit-literature Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 125 | mollydanielsson |
August 29, 2014 16:56
| over 9 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren LabelingLabel sample bottles with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context.
Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samples and compareAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Add the spectrum of your unknown sample and see which of the others it is closest to. Calibration and intensityYour spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. If your scans were not made with the same amount of light, or if the spectrometer was not aligned the same way, two scans of the same material may not appear the same on your plot -- which would make it hard or impossible to see your sample is a good match or not. Some research suggests that such spectra should be comparable if their area is equalized -- this remains to be demonstrated Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit LiteratureGiger, Walter, and Max Blumer. "Polycyclic aromatic hydrocarbons in the environment. Isolation and characterization by chromatography, visible, ultraviolet, and mass spectrometry." Analytical chemistry 46.12 (1974): 1663-1671. http://pubs.acs.org/doi/abs/10.1021/ac60348a036 Pharr, Daniel Y., J. Keith McKenzie, and Aaron B. Hickman. "Fingerprinting petroleum contamination using synchronous scanning fluorescence spectroscopy." Groundwater 30.4 (1992): 484-489. http://onlinelibrary.wiley.com/doi/10.1111/j.1745-6584.1992.tb01523.x/abstract Ryder, Alan G. "Analysis of crude petroleum oils using fluorescence spectroscopy." Reviews in Fluorescence 2005. Springer US, 2005. 169-198. http://link.springer.com/chapter/10.1007%2F0-387-23690-2_8 Fan, Chi-Yuan, S. Krishnamurthy, and Chien T. Chen. "A critical review of analytical approaches for petroleum contaminated soil." ASTM SPECIAL TECHNICAL PUBLICATION 1221 (1994): 61-61. (via Google Books) "Molecular Probes Handbook" by LifeTechnologies.com - http://www.lifetechnologies.com/us/en/home/references/molecular-probes-the-handbook/introduction-to-fluorescence-techniques.html Kavanagh, Richard J., et al. "Detecting oil sands process-affected waters in the Alberta oil sands region using synchronous fluorescence spectroscopy." Chemosphere 76.1 (2009): 120-126. (may be closed access but @warren has a copy) http://scholar.google.com/scholar?cluster=14373696302921970489&hl=en&as_sdt=0,22 Christensen, Jan H., et al. "Characterization and matching of oil samples using fluorescence spectroscopy and parallel factor analysis." Analytical chemistry 77.7 (2005): 2210-2217. (may be closed access but @warren has a copy) http://scholar.google.com/scholar?cluster=10865678698430550672&hl=en&as_sdt=0,22 Agostino, Patrick N., Rufus J. LeBlanc Jr, and Victor T. Jones III. "Assessment of subsurface hydrocarbon contamination resulting from multiple releases at six former bulk-fuel storage and distribution terminals, Austin, Texas: A case study." Surface Exploration Case Histories: Applications of Geochemistry, Magnetics and Remote Sensing. D. Schumacher and LA LeSchack, eds. AAPG Studies in Geology No. 48 and SEG Geophysical References Series 11 (2002): 299-325. (may be closed access but @warren has a copy) http://archives.datapages.com/data/specpubs/study48/st48ch11/st48ch11.htm Closed articles we haven't been able to access: Kershaw, J. R., and J. C. Fetzer. "The room temperature fluorescence analysis of polycyclic aromatic compounds in petroleum and related materials." Polycyclic Aromatic Compounds 7.4 (1995): 253-268. http://scholar.google.com/scholar?cluster=11103245098655707138&hl=en&as_sdt=0,22 Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 124 | warren |
August 12, 2014 19:27
| over 9 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren LabelingLabel sample bottles with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context.
Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samples and compareAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Add the spectrum of your unknown sample and see which of the others it is closest to. Calibration and intensityYour spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. If your scans were not made with the same amount of light, or if the spectrometer was not aligned the same way, two scans of the same material may not appear the same on your plot -- which would make it hard or impossible to see your sample is a good match or not. Some research suggests that such spectra should be comparable if their area is equalized -- this remains to be demonstrated Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit LiteratureGiger, Walter, and Max Blumer. "Polycyclic aromatic hydrocarbons in the environment. Isolation and characterization by chromatography, visible, ultraviolet, and mass spectrometry." Analytical chemistry 46.12 (1974): 1663-1671. http://pubs.acs.org/doi/abs/10.1021/ac60348a036 Pharr, Daniel Y., J. Keith McKenzie, and Aaron B. Hickman. "Fingerprinting petroleum contamination using synchronous scanning fluorescence spectroscopy." Groundwater 30.4 (1992): 484-489. http://onlinelibrary.wiley.com/doi/10.1111/j.1745-6584.1992.tb01523.x/abstract Ryder, Alan G. "Analysis of crude petroleum oils using fluorescence spectroscopy." Reviews in Fluorescence 2005. Springer US, 2005. 169-198. http://link.springer.com/chapter/10.1007%2F0-387-23690-2_8 Fan, Chi-Yuan, S. Krishnamurthy, and Chien T. Chen. "A critical review of analytical approaches for petroleum contaminated soil." ASTM SPECIAL TECHNICAL PUBLICATION 1221 (1994): 61-61. (via Google Books) "Molecular Probes Handbook" by LifeTechnologies.com - http://www.lifetechnologies.com/us/en/home/references/molecular-probes-the-handbook/introduction-to-fluorescence-techniques.html Kavanagh, Richard J., et al. "Detecting oil sands process-affected waters in the Alberta oil sands region using synchronous fluorescence spectroscopy." Chemosphere 76.1 (2009): 120-126. (may be closed access but @warren has a copy) http://scholar.google.com/scholar?cluster=14373696302921970489&hl=en&as_sdt=0,22 Christensen, Jan H., et al. "Characterization and matching of oil samples using fluorescence spectroscopy and parallel factor analysis." Analytical chemistry 77.7 (2005): 2210-2217. (may be closed access but @warren has a copy) http://scholar.google.com/scholar?cluster=10865678698430550672&hl=en&as_sdt=0,22 Agostino, Patrick N., Rufus J. LeBlanc Jr, and Victor T. Jones III. "Assessment of subsurface hydrocarbon contamination resulting from multiple releases at six former bulk-fuel storage and distribution terminals, Austin, Texas: A case study." Surface Exploration Case Histories: Applications of Geochemistry, Magnetics and Remote Sensing. D. Schumacher and LA LeSchack, eds. AAPG Studies in Geology No. 48 and SEG Geophysical References Series 11 (2002): 299-325. (may be closed access but @warren has a copy) http://archives.datapages.com/data/specpubs/study48/st48ch11/st48ch11.htm Closed articles we haven't been able to access: Kershaw, J. R., and J. C. Fetzer. "The room temperature fluorescence analysis of polycyclic aromatic compounds in petroleum and related materials." Polycyclic Aromatic Compounds 7.4 (1995): 253-268. http://scholar.google.com/scholar?cluster=11103245098655707138&hl=en&as_sdt=0,22 Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 123 | warren |
August 12, 2014 18:59
| over 9 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren LabelingLabel sample bottles with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context.
Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samples and compareAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Add the spectrum of your unknown sample and see which of the others it is closest to. Calibration and intensityYour spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. If your scans were not made with the same amount of light, or if the spectrometer was not aligned the same way, two scans of the same material may not appear the same on your plot -- which would make it hard or impossible to see your sample is a good match or not. Some research suggests that such spectra should be comparable if their area is equalized -- this remains to be demonstrated Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit LiteratureGiger, Walter, and Max Blumer. "Polycyclic aromatic hydrocarbons in the environment. Isolation and characterization by chromatography, visible, ultraviolet, and mass spectrometry." Analytical chemistry 46.12 (1974): 1663-1671. http://pubs.acs.org/doi/abs/10.1021/ac60348a036 Pharr, Daniel Y., J. Keith McKenzie, and Aaron B. Hickman. "Fingerprinting petroleum contamination using synchronous scanning fluorescence spectroscopy." Groundwater 30.4 (1992): 484-489. http://onlinelibrary.wiley.com/doi/10.1111/j.1745-6584.1992.tb01523.x/abstract Ryder, Alan G. "Analysis of crude petroleum oils using fluorescence spectroscopy." Reviews in Fluorescence 2005. Springer US, 2005. 169-198. http://link.springer.com/chapter/10.1007%2F0-387-23690-2_8 Fan, Chi-Yuan, S. Krishnamurthy, and Chien T. Chen. "A critical review of analytical approaches for petroleum contaminated soil." ASTM SPECIAL TECHNICAL PUBLICATION 1221 (1994): 61-61. (via Google Books) "Molecular Probes Handbook" by LifeTechnologies.com - http://www.lifetechnologies.com/us/en/home/references/molecular-probes-the-handbook/introduction-to-fluorescence-techniques.html Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 122 | warren |
August 12, 2014 15:36
| over 9 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren LabelingLabel sample bottles with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context.
Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samples and compareAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Add the spectrum of your unknown sample and see which of the others it is closest to. Calibration and intensityYour spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. If your scans were not made with the same amount of light, or if the spectrometer was not aligned the same way, two scans of the same material may not appear the same on your plot -- which would make it hard or impossible to see your sample is a good match or not. Some research suggests that such spectra should be comparable if their area is equalized -- this remains to be demonstrated Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit LiteratureGiger, Walter, and Max Blumer. "Polycyclic aromatic hydrocarbons in the environment. Isolation and characterization by chromatography, visible, ultraviolet, and mass spectrometry." Analytical chemistry 46.12 (1974): 1663-1671. http://pubs.acs.org/doi/abs/10.1021/ac60348a036 Pharr, Daniel Y., J. Keith McKenzie, and Aaron B. Hickman. "Fingerprinting petroleum contamination using synchronous scanning fluorescence spectroscopy." Groundwater 30.4 (1992): 484-489. http://onlinelibrary.wiley.com/doi/10.1111/j.1745-6584.1992.tb01523.x/abstract Ryder, Alan G. "Analysis of crude petroleum oils using fluorescence spectroscopy." Reviews in Fluorescence 2005. Springer US, 2005. 169-198. http://link.springer.com/chapter/10.1007%2F0-387-23690-2_8 "Molecular Probes Handbook" by LifeTechnologies.com - http://www.lifetechnologies.com/us/en/home/references/molecular-probes-the-handbook/introduction-to-fluorescence-techniques.html Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 121 | bsugar |
August 11, 2014 23:25
| over 9 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren LabelingLabel sample bottles with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context.
Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samples and compareAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Add the spectrum of your unknown sample and see which of the others it is closest to. Calibration and intensityYour spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. If your scans were not made with the same amount of light, or if the spectrometer was not aligned the same way, two scans of the same material may not appear the same on your plot -- which would make it hard or impossible to see your sample is a good match or not. Some research suggests that such spectra should be comparable if their area is equalized -- this remains to be demonstrated Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit Literature reviewGiger, Walter, and Max Blumer. "Polycyclic aromatic hydrocarbons in the environment. Isolation and characterization by chromatography, visible, ultraviolet, and mass spectrometry." Analytical chemistry 46.12 (1974): 1663-1671. http://pubs.acs.org/doi/abs/10.1021/ac60348a036 Pharr, Daniel Y., J. Keith McKenzie, and Aaron B. Hickman. "Fingerprinting petroleum contamination using synchronous scanning fluorescence spectroscopy." Groundwater 30.4 (1992): 484-489. http://onlinelibrary.wiley.com/doi/10.1111/j.1745-6584.1992.tb01523.x/abstract Ryder, Alan G. "Analysis of crude petroleum oils using fluorescence spectroscopy." Reviews in Fluorescence 2005. Springer US, 2005. 169-198. http://link.springer.com/chapter/10.1007%2F0-387-23690-2_8 Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 120 | warren |
August 04, 2014 19:27
| almost 10 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren LabelingLabel sample bottles with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context.
Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samples and compareAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Add the spectrum of your unknown sample and see which of the others it is closest to. Calibration and intensityYour spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. If your scans were not made with the same amount of light, or if the spectrometer was not aligned the same way, two scans of the same material may not appear the same on your plot -- which would make it hard or impossible to see your sample is a good match or not. Some research suggests that such spectra should be comparable if their area is equalized -- this remains to be demonstrated Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit Literature reviewGiger, Walter, and Max Blumer. "Polycyclic aromatic hydrocarbons in the environment. Isolation and characterization by chromatography, visible, ultraviolet, and mass spectrometry." Analytical chemistry 46.12 (1974): 1663-1671. http://pubs.acs.org/doi/abs/10.1021/ac60348a036 Pharr, Daniel Y., J. Keith McKenzie, and Aaron B. Hickman. "Fingerprinting petroleum contamination using synchronous scanning fluorescence spectroscopy." Groundwater 30.4 (1992): 484-489. http://onlinelibrary.wiley.com/doi/10.1111/j.1745-6584.1992.tb01523.x/abstract Ryder, Alan G. "Analysis of crude petroleum oils using fluorescence spectroscopy." Reviews in Fluorescence 2005. Springer US, 2005. 169-198. http://link.springer.com/chapter/10.1007%2F0-387-23690-2_8 Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 119 | mathew |
July 30, 2014 21:51
| almost 10 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren LabelingLabel sample bottles with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context. [image of bottle with id label next to notebook with extra details] Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samples and compareAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Add the spectrum of your unknown sample and see which of the others it is closest to. Calibration and intensityYour spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. If your scans were not made with the same amount of light, or if the spectrometer was not aligned the same way, two scans of the same material may not appear the same on your plot -- which would make it hard or impossible to see your sample is a good match or not. Some research suggests that such spectra should be comparable if their area is equalized -- this remains to be demonstrated Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit Literature reviewGiger, Walter, and Max Blumer. "Polycyclic aromatic hydrocarbons in the environment. Isolation and characterization by chromatography, visible, ultraviolet, and mass spectrometry." Analytical chemistry 46.12 (1974): 1663-1671. http://pubs.acs.org/doi/abs/10.1021/ac60348a036 Pharr, Daniel Y., J. Keith McKenzie, and Aaron B. Hickman. "Fingerprinting petroleum contamination using synchronous scanning fluorescence spectroscopy." Groundwater 30.4 (1992): 484-489. http://onlinelibrary.wiley.com/doi/10.1111/j.1745-6584.1992.tb01523.x/abstract Ryder, Alan G. "Analysis of crude petroleum oils using fluorescence spectroscopy." Reviews in Fluorescence 2005. Springer US, 2005. 169-198. http://link.springer.com/chapter/10.1007%2F0-387-23690-2_8 Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 118 | warren |
July 30, 2014 20:33
| almost 10 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg LabelingLabel the bottle with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context. [image of bottle with id label next to notebook with extra details] ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samples and compareAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Add the spectrum of your unknown sample and see which of the others it is closest to. Calibration and intensityYour spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. If your scans were not made with the same amount of light, or if the spectrometer was not aligned the same way, two scans of the same material may not appear the same on your plot -- which would make it hard or impossible to see your sample is a good match or not. Some research suggests that such spectra should be comparable if their area is equalized -- this remains to be demonstrated Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit Literature reviewGiger, Walter, and Max Blumer. "Polycyclic aromatic hydrocarbons in the environment. Isolation and characterization by chromatography, visible, ultraviolet, and mass spectrometry." Analytical chemistry 46.12 (1974): 1663-1671. http://pubs.acs.org/doi/abs/10.1021/ac60348a036 Pharr, Daniel Y., J. Keith McKenzie, and Aaron B. Hickman. "Fingerprinting petroleum contamination using synchronous scanning fluorescence spectroscopy." Groundwater 30.4 (1992): 484-489. http://onlinelibrary.wiley.com/doi/10.1111/j.1745-6584.1992.tb01523.x/abstract Ryder, Alan G. "Analysis of crude petroleum oils using fluorescence spectroscopy." Reviews in Fluorescence 2005. Springer US, 2005. 169-198. http://link.springer.com/chapter/10.1007%2F0-387-23690-2_8 Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 117 | warren |
July 24, 2014 20:15
| almost 10 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg LabelingLabel the bottle with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context. [image of bottle with id label next to notebook with extra details] ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samplesAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Your spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit Literature reviewGiger, Walter, and Max Blumer. "Polycyclic aromatic hydrocarbons in the environment. Isolation and characterization by chromatography, visible, ultraviolet, and mass spectrometry." Analytical chemistry 46.12 (1974): 1663-1671. http://pubs.acs.org/doi/abs/10.1021/ac60348a036 Pharr, Daniel Y., J. Keith McKenzie, and Aaron B. Hickman. "Fingerprinting petroleum contamination using synchronous scanning fluorescence spectroscopy." Groundwater 30.4 (1992): 484-489. http://onlinelibrary.wiley.com/doi/10.1111/j.1745-6584.1992.tb01523.x/abstract Ryder, Alan G. "Analysis of crude petroleum oils using fluorescence spectroscopy." Reviews in Fluorescence 2005. Springer US, 2005. 169-198. http://link.springer.com/chapter/10.1007%2F0-387-23690-2_8 Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 116 | warren |
July 23, 2014 20:30
| almost 10 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg LabelingLabel the bottle with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context. [image of bottle with id label next to notebook with extra details] ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samplesAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Your spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit Literature reviewGiger, Walter, and Max Blumer. "Polycyclic aromatic hydrocarbons in the environment. Isolation and characterization by chromatography, visible, ultraviolet, and mass spectrometry." Analytical chemistry 46.12 (1974): 1663-1671. http://pubs.acs.org/doi/abs/10.1021/ac60348a036 Pharr, Daniel Y., J. Keith McKenzie, and Aaron B. Hickman. "Fingerprinting petroleum contamination using synchronous scanning fluorescence spectroscopy." Groundwater 30.4 (1992): 484-489. http://onlinelibrary.wiley.com/doi/10.1111/j.1745-6584.1992.tb01523.x/abstract Ryder, Alan G. "Analysis of crude petroleum oils using fluorescence spectroscopy." Reviews in Fluorescence 2005. Springer US, 2005. 169-198. http://link.springer.com/chapter/10.1007%2F0-387-23690-2_8 Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 115 | warren |
July 23, 2014 18:20
| almost 10 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg LabelingLabel the bottle with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context. [image of bottle with id label next to notebook with extra details] ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samplesAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Your spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit Literature reviewGiger, Walter, and Max Blumer. "Polycyclic aromatic hydrocarbons in the environment. Isolation and characterization by chromatography, visible, ultraviolet, and mass spectrometry." Analytical chemistry 46.12 (1974): 1663-1671. http://pubs.acs.org/doi/abs/10.1021/ac60348a036 Pharr, Daniel Y., J. Keith McKenzie, and Aaron B. Hickman. "Fingerprinting petroleum contamination using synchronous scanning fluorescence spectroscopy." Groundwater 30.4 (1992): 484-489. http://onlinelibrary.wiley.com/doi/10.1111/j.1745-6584.1992.tb01523.x/abstract Ryder, Alan G. "Analysis of crude petroleum oils using fluorescence spectroscopy." Reviews in Fluorescence 2005. Springer US, 2005. 169-198. http://link.springer.com/chapter/10.1007%2F0-387-23690-2_8 Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 114 | warren |
July 23, 2014 18:20
| almost 10 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg LabelingLabel the bottle with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context. [image of bottle with id label next to notebook with extra details] ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions.
A variety of prototypes for scanning fluorescence in oil samples. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samplesAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Your spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit Literature reviewGiger, Walter, and Max Blumer. "Polycyclic aromatic hydrocarbons in the environment. Isolation and characterization by chromatography, visible, ultraviolet, and mass spectrometry." Analytical chemistry 46.12 (1974): 1663-1671. http://pubs.acs.org/doi/abs/10.1021/ac60348a036 Pharr, Daniel Y., J. Keith McKenzie, and Aaron B. Hickman. "Fingerprinting petroleum contamination using synchronous scanning fluorescence spectroscopy." Groundwater 30.4 (1992): 484-489. http://onlinelibrary.wiley.com/doi/10.1111/j.1745-6584.1992.tb01523.x/abstract Ryder, Alan G. "Analysis of crude petroleum oils using fluorescence spectroscopy." Reviews in Fluorescence 2005. Springer US, 2005. 169-198. http://link.springer.com/chapter/10.1007%2F0-387-23690-2_8 Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert | |
| 113 | warren |
July 23, 2014 18:08
| almost 10 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg LabelingLabel the bottle with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context. [image of bottle with id label next to notebook with extra details] ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samplesAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Your spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit Literature reviewGiger, Walter, and Max Blumer. "Polycyclic aromatic hydrocarbons in the environment. Isolation and characterization by chromatography, visible, ultraviolet, and mass spectrometry." Analytical chemistry 46.12 (1974): 1663-1671. http://pubs.acs.org/doi/abs/10.1021/ac60348a036 Pharr, Daniel Y., J. Keith McKenzie, and Aaron B. Hickman. "Fingerprinting petroleum contamination using synchronous scanning fluorescence spectroscopy." Groundwater 30.4 (1992): 484-489. http://onlinelibrary.wiley.com/doi/10.1111/j.1745-6584.1992.tb01523.x/abstract Ryder, Alan G. "Analysis of crude petroleum oils using fluorescence spectroscopy." Reviews in Fluorescence 2005. Springer US, 2005. 169-198. http://link.springer.com/chapter/10.1007%2F0-387-23690-2_8 Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
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| 112 | warren |
July 23, 2014 18:07
| almost 10 years ago
IntroductionThe Oil Testing Kit is an open source Do-It-Yourself kit which attempts to make it possible to identify oil pollution by type. This means matching a suspected sample with a known sample of crude oil, motor oil, heating oil, or other petroleum-based contaminant using a homemade fluorescence spectrometer. A spectrometer enables you to precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light, as shown above. Collect, Scan, CompareThe process of testing for oils can be described in three overall steps;
Here we will discuss and illustrate these steps in depth -- but keep in mind this process is always evolving. See the Challenges section for ways to get involved and contribute. CollectLocating samplesOriginally, we focused on tar balls which were washing up on US Gulf Coast shorelines following the BP oil spill. These ranged from hard black lumps to orange residue. But oil contamination takes many forms, from residue around a street drain, to a sheen or buildup on the surface of the water. Here are some examples:
Left to right: dried oil on rocks in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, oil residue in the ocean in 2010, Louisiana coast by Cesar Harada CC-BY-NC-SA, Oil tanker leak on tracks beside Mississippi River, by @marlokeno, swabbing a street grate by @warren Preparing samplesUse a cotton swab or small brush, dipped in mineral oil, to break up some of the material and dissolve it in a small, square-sided glass jar of mineral or baby oil. Wear gloves before handling suspected pollutants. You may need to rub the sample for a while to get it to dissolve. If it does not dissolve, there may be more aggressive ways to dissolve it. Where possible, try not to put too much sand or other stuff in the jar. It's a good idea to keep extra samples (dry, as you found them, not in mineral oil) in glass jars, stored in a cool dark place, as there may be an opportunity to test them later with more expensive, official means (see Validate your results below).
Seal the bottle tightly with the cap. You can then gently turn it over a few times to get the residue to dissolve -- it may take some time before the mineral oil takes on a distinct but faint yellowish hue. You may then have to wait for the sediment to settle out. You want the liquid to be quite transparent, with the chunky stuff settled to the bottom. ConcentrationOne big issue is getting the correct concentration of sample dissolved. If it's too little, we may not be able to get it to glow under UV light. Too much and it could be too dark for the light to be visible in the bottle. Ideally we'd like to have the same concentration in each sample bottle, but determining this is very difficult as the samples may be mixed, so they can't easily be weighed. We recommend going by how dark they are -- try for a color similar to very dilute tea:
This sample by @eustatic is too dark for the laser to get through: https://farm4.staticflickr.com/3725/9711572372_3aa638cf46.jpg LabelingLabel the bottle with the date, time, and location. If you also give it a unique number, any other information can be kept in a notebook next to that number, such as further notes on the location and its condition. Take a photo of the sample with your label, in the place you found the sample, for context. [image of bottle with id label next to notebook with extra details] ScanNow that your sample is prepared, you may be able to get it to fluoresce or glow by shining an ultraviolet light through it. We have had good results using a blue/UV laser, a 405 nanometer laser which is the same as found in a Blu-Ray player. See the parts list below for where to buy one. Strong UV LEDs can also work, but are not as bright. They are, however, easier to line up with a spectrometer's opening slit.
Don't look at the laser too much, as it can hurt your eyes, even if you're not pointing it directly at your eye!
Note that the laser will have a purple-ish color by itself (as seen in the lead image at the top of the page) -- this is not fluorescence, but just scattering of the laser light. What you're looking for is any other color -- whitish, bluish, greenish -- which is not from the laser, but is produced in the material itself as it's excited by the UV light. To measure precisely the colors that are being produced, we will use a spectrometer.
SpectrometryColored light is often a blend of different colors. A spectrometer is a device which splits those colors apart, like a prism, and measures the strength of each color. A typical output of a spectrometer looks like this spectrum of the daytime sky, with the actual light spectrum at the top and the graph of wavelength (horizontal axis) and intensity (vertical axis) below:
While there are many ways to use a spectrometer, when we scan the fluorescence from an oil sample, we can clearly see the laser color, or wavelength, which is only in a narrow range around 405 nanometers, to the left:
All the remaining light, to the right of that tall peak, is produced by the excited material in the sample. The shape of that curve can be matched against other samples to help us identify what ours is. But first, we'll need a spectrometer. This section is under construction.
Construct a spectrometerPublic Lab first began developing cheap spectrometers in the winter of 2010, after the Deepwater Horizon oil disaster in the Gulf of Mexico. Since then we've made enormous progress and have a variety of designs for less than $100, including:
Of course, the plans for all of these are on the Public Lab website and are open source hardware designs, so you can always make your own -- the kits are intended to help you get started. However, none of these designs currently includes a place to put a sample, or a laser to illuminate it -- they were designed before we developed that technique. So we are currently working on a new version, and need your help! See the Challenges section for more ways to get involved. For now, you can purchase the add-on "Alpha" Oil Testing Kit (see parts list to assemble your own) in combination with the existing Desktop Spectrometry Kit, which is what was used in the examples on this page. See the main spectrometer page for build instructions. Illuminate the sampleWhether you use the Alpha Oil Test Kit, or one of the prototype designs recently published, the basics are that you need to illuminate your sample with a laser beam perpendicularly to the direction your spectrometer is pointing, and to align it so that you can see enough light using the software at SpectralWorkbench.org.
Unlike the illustration above, you'll want to do it in a dark box, where ambient light won't interfere with your readings. The illustration shows scanning a control sample at the same time, but this may not be necessary if everything is consistent between scans. You'll want to see something like this in the software.
If you don't, but you can visibly see fluorescence (see below for examples), try moving the laser up and down a bit to get it to align. You want the curve to the left of the tall peak (which is the laser) to be mostly between 25% and 75% intensity, so it's not "clipping" by being too bright but you're getting enough light to see a clear shape amongst the noise. This process of getting enough light into the spectrometer needs improvement -- see the Challenges section to help out. Refine your techniqueOnce you get a basic scan, save and label it, but consider some of these techniques to improve your data collection:
Once you're confident that your sampling is consistent and rigorous, you're ready to start comparing the data you've collected. CompareWhen identifying an oil, we are hoping to measure the color of fluorescence of the Poly-Aromatic Hydrocarbons (PAHs) in the sample. The best way to identify a sample would be to compare it to a selection of similarly-prepared known reference materials. For example, if you have unknown X, you could compare it to both: A) a known sample of crude oil and B) a known uncontaminated sample of material (perhaps soil) to see which it matches best.
Which is it more like? Ideally, it should be compared to a range of possible references. For example, if it's possible the sample is heating oil or motor oil, you could compare it to similarly prepared samples of those as well. Some research has shown that vitamins A and E can produce fluorescence similar to petroleum products.
Plot your samplesAdd all your scans to a set, so they can be viewed together, and you can see the subtle color differences as graphed lines. Your spectrometer should be calibrated and the very tall peaks from the laser light should align if this has been done correctly. If your scans are too dim (mostly under <25%) or too bright (hitting the 100% ceiling), you may want to try re-running them. Positive and negative controlsThink critically about your testing and how it might have gone wrong. Could you have made mistakes, or is the match you've found between your unknown sample and your references not good enough? Could another material produce the same color spectrum as your suspected contaminant, and fool your test? (See this research on Vitamins E and A causing such false positives). Validate your resultsAn extra step that may give your work more credibility is to submit a few of your samples for analysis to a lab, or to use other tests to confirm your results. Alternatively, if you know other testing has occurred, you can try to extend its results by re-testing the same site or samples, correlating your results with the previous test, and performing your own tests over a larger area or on more sites, or over a longer time span. PublishAsk others to critique your work or help you refine it on the plots-spectroscopy discussion list or by posting a research note thoroughly describing your results. Even if your work is not done, it's a great idea to share and solicit feedback on your plan before, during, and after you've done the work. You may be able to build on previous work on the website, and your work will help others who are seeking to perform similar tests. Dissolving samplesWe use mineral oil as it's non-toxic and cheap, and can be purchased in most pharmacies as either mineral oil or "baby oil". However, some samples may be hard enough that they don't dissolve readily, and more aggressive solvents may be able to dissolve these, such as methanol or denatured alcohol. These are not as safe to handle, however, so we advise caution if you attempt this. Please post a research note if you attempt this, as it is an unexplored area. ChallengesThis document, and this methodology, is still under active development. What you see on this page is only the best attempt so far at collating and presenting the work of Public Lab contributors to date. Some of the challenges that remain include:
Be sure to share your research as you tackle these questions -- publish early and often! Remember that every additional step can add complexity and cost to the process, so always keep in mind what such steps achieve, and balance that against the potential barrier to entry they cause. VariationsThere are many variations of the process which could be useful but are not essential. These include:
Many of these may be future goals of the project, but we are focusing on our primary use case of collecting contaminated soil or residue from the ground, dissolving it in mineral oil, and illuminating it with UV in a spectrometer. Alpha programWe've sent out about 20 prototype "alpha" kits to people around the US to give the oil test kit a try, and refine it to get ready for a bigger release. If you have one please share what you've done with it and post any ideas, feedback, complaints, suggestions, questions and modifications you have by using this button:
Post about your alpha oil testing kit Literature reviewGiger, Walter, and Max Blumer. "Polycyclic aromatic hydrocarbons in the environment. Isolation and characterization by chromatography, visible, ultraviolet, and mass spectrometry." Analytical chemistry 46.12 (1974): 1663-1671. http://pubs.acs.org/doi/abs/10.1021/ac60348a036 Pharr, Daniel Y., J. Keith McKenzie, and Aaron B. Hickman. "Fingerprinting petroleum contamination using synchronous scanning fluorescence spectroscopy." Groundwater 30.4 (1992): 484-489. http://onlinelibrary.wiley.com/doi/10.1111/j.1745-6584.1992.tb01523.x/abstract Ryder, Alan G. "Analysis of crude petroleum oils using fluorescence spectroscopy." Reviews in Fluorescence 2005. Springer US, 2005. 169-198. http://link.springer.com/chapter/10.1007%2F0-387-23690-2_8 Parts listIn progress: these are links to where you can buy parts to assemble your own oil testing kit
Resources |
Revert |
