Update: Alpha kits are now available: http://store.publiclab.org/products/spectrometry-sampling-kit
What I want to do
We are developing a "companion kit" for the Public Lab Spectrometer tailored specifically for detecting and identifying petroleum contamination -- mostly for solid residue and tarballs at this point, but hopefully applicable for sheens too at some point.
My attempt and results
Based on a variety of experiments over the past few months (mainly this initial test and this series of more careful tests at Parts & Crafts), we are getting more confident about our ability to detect and identify types of oil contamination; that is, to distinguish motor, heating, and crude oils.
Long story short, you can shine a blue (405nm) laser through a jar of mineral oil which has had a very small amount of the suspected oil dissolved in it, and it'll fluoresce different colors depending on the type of oil it is.
To push this work forward, this new kit will include all of the following, to help people who want to contribute (or just try it out) with all the basic tools and materials. This is supposed to be paired with one of our existing spectrometers, by the way.
- 5oz mineral oil (baby oil -- the added fragrance doesn't fluoresce): $3 - http://www.amazon.com/Johnson-Baby-Oil-Kids-Ounce/dp/B000GCJM06/
- an eyedropper: $0.05 0 http://www.sciplus.com/p/CAP-WDROPPER_39038
- a 405nm blue/violet laser pen: $3 http://www.alibaba.com/product-gs/700677050/well_tested_405_nm_blue_laser.html, or http://www.ebay.com/itm/like/350812684726?lpid=82 to buy just one cuvettes
- 4 flat-sided jars: $0.35 each - http://www.sciplus.com/p/WHITCAP-BOTTLE_48212
- cotton swabs: $0.10
- olive oil test sample: $0.17
- paper instructions (yet to be made)
The basic instructions will be something like:
- Put on latex or nitrile gloves
- Wet a cotton swab with mineral oil
- Rub it on the sample -- a suspected tarball or lump of oily residue -- until it gets brownish (it could take a little while for it to dissolve)
- Dip the dirty swab (that's like a pirate insult... :-P) in one of the square bottles which has been filled 2/3 with mineral oil, and repeatedly and gently dunk it until the brown stuff dissolves and "taints" the mineral oil.
- Keep dunking until it looks like a very very weak tea -- so you can see the coloration. We need to come up with a standard way to determine how dark... maybe a printed comparison strip?
- Cap the square jar and throw away the cotton swab (bag it if it's really gross).
- Throw away the gloves and wash your hands
Then, inside your spectrometer box (to reduce stray light and to protect your eyes from the laser light):
- Without looking at the laser light directly (it's bad for your eyes!!!), shine the laser through a hole in your box, so the laser shines through your jar perpendicular to the spectrometer opening. We'll illustrate this better but look at the Parts & Crafts note above.
- Move the laser up and down until you see both the bright laser peak on your SpectralWorkbench.org graph, as well as the broader range of colors that are the fluorescence.
Really do check out the photos from the Parts & Crafts tests mentioned above to see more detail!
Questions and next steps
This list of materials has to be refined a bit, and maybe adjusted based on prices and availability. I added the olive oil packets because extra virgin olive oil will fluoresce because of the chlorophyll in it -- a good, non-toxic test case.
We also have to be sure people use the laser safely; only inside the box, and never looking at the light, let alone pointing it in their eye or something.
The methodology may need to be improved or adapted. Some samples may not dissolve readily in mineral oil, and methanol (denatured alcohol, from the hardware store) could be an alternative, though it's toxic.
Why I'm interested
Once we get people using this sort of kit, even if it still needs a lot of improvement, we should start making much faster progress at identifying oil samples. To date, lots of folks on SpectralWorkbench.org and in the Public Lab community are still using light bulbs for absorption spectroscopy, and many new spectrometer makers are not sure what to do once they've calibrated their spectrometer. We should get as many folks as possible doing this kind of laser oil testing, so this kit is a high priority.