Spectrometry Sampling

**How do you test liquid or solid samples with your [DIY Spectrometer](/wiki/spectrometer)?** Read about ways to prepare and scan samples here, and [read about different tests you can do with your spectrometer](/wiki/spectrometry-activities). ## Questions [questions:spectrometry-sampling] **** ## Sample containers What do you store liquid samples in? A good sample container has flat sides, so you can shine lights (and lasers) through it without lots of reflections. There are lots of different [affordable test tubes on Amazon](https://www.amazon.com/s/?field-keywords=test%20tubes), but they're mostly round. Flat-sided test tubes are often called **cuvettes** and are specifically for spectrometry. It's also good to have the light travel through a consistent amount of the sample -- many cuvettes (traditional spectrometry sample containers) are 1cm x 1cm, so the light always goes through 1cm of the sample. [![dropper.jpg](https://i.publiclab.org/system/images/photos/000/001/730/medium/dropper.jpg)](https://i.publiclab.org/system/images/photos/000/001/730/original/dropper.jpg) [![Cuvette_with_penny.jpg](https://i.publiclab.org/system/images/photos/000/001/731/medium/Cuvette_with_penny.jpg)](https://i.publiclab.org/system/images/photos/000/001/731/original/Cuvette_with_penny.jpg) _A square-sided bottle, left, and a cuvette, right (photo from [Wikipedia](http://simple.wikipedia.org/wiki/Cuvette))._ Unfortunately, we've found that cuvettes with plastic stoppers will leak when filled with oil and not kept upright (for example if you travel with them). A really nice source of completely sealable rectangular 1/4 oz glass jars which are pretty perfect for sampling can be found for $3.50 for a ten-pack here (see image below of 2 on top of a flashlight): http://www.sciplus.com/p/WHITCAP-BOTTLE_48212 **Other sample container options** * $20 (w/ shipping) 100x plastic (polystyrene) cuvettes: http://www.amazon.com/Cuvette-Polystyrene-Macro-2-5Ml-4-5Ml/dp/B008H5XJ9E/ (no caps) * $9 100x cuvette caps: http://www.amazon.com/Azzota-A920-Cuvettes-Caps-100/dp/B005YOJPLC/ * $22 Quartz cuvette (transparent in farther UV range): http://www.amazon.com/Quartz-Cuvette-standard-10mm-spectrometer/dp/B00DWXFIS6/ **** ## Water sampling Water is usually very clear in small amounts -- even murky water in a small container will look pretty transparent. That makes it hard to measure with spectrometry unless you shine light through a *lot* of it. But some tests have been done -- see this example of a scan of water from the Charles River before and after 7 days of settling, by [Jeff Hecht](https://spectralworkbench.org/sets/show/330): [![charles-river.png](https://i.publiclab.org/system/images/photos/000/001/732/large/charles-river.png)](https://spectralworkbench.org/sets/show/330) **** ## Oil sampling However, most research in Public Lab to date has focused on oil spectroscopy -- attempting to identify petroleum residue in sediments. [![IMG_20140722_230007_2.jpg](https://i.publiclab.org/system/images/photos/000/005/452/large/IMG_20140722_230007_2.jpg)](https://i.publiclab.org/system/images/photos/000/005/452/original/IMG_20140722_230007_2.jpg) To identify oil contamination, we [have been attempting](/tag/fluorescence) to illuminate oil samples with UV flashlights and green lasers, which can make some oils fluoresce, or glow, as pictured above. The basics of sample preparation for oil identification are still being refined, but our best practices to date can be found on the [Oil Testing Kit page](/wiki/oil-testing-kit) **** [![Flame spectroscopy](https://i.publiclab.org/system/images/photos/000/001/634/medium/IMG_1794.JPG)](https://i.publiclab.org/system/images/photos/000/001/634/original/IMG_1794.JPG) _Burning potato chips to measure the sodium emission spectrum from the NaCl (salt)._ ## Flame spectroscopy Another type of spectrometry which involves measuring the light of a flame and can detect specific elements (not molecules) as they emit light at very specific "peaks" -- narrow wavelength bands. Besides flames, these "emission lines" can be produced by exposing gases or sometimes liquids to UV light, lasers, or electric fields (as in a fluorescent bulb). The fluorescent bulb spectrum [you get when calibrating](/wiki/spectral-workbench-calibration) is an example of a mercury emission spectrum. Emission lines are produced by atoms, not whole molecules (the latter produce absorption lines, which we might still be able to detect since we have the flame -- a good broad-spectrum light source -- but that is just a theory at this point). So sulfur and carbon are possible targets, but we won't be able to distinguish CO2 from CO. **Basic setup:** For a more complete description, please read about the "flare spectroscopy activity" below, however, the basic setup involves simply pointing a spectrometer at a flame (which can be difficult to line up if the flame is far away), and later comparing any peaks to known peak locations of looked-for elements. We are compiling a collection of such known elements by importing "idealized" spectra from the NIST database, a process which you can [read more about here](/notes/warren/08-13-2013/importing-spectra-from-nist-and-webmineral-com-to-spectral-workbench). Read more about flame spectroscopy: - [Flare spectroscopy activity](/wiki/flare-spectroscopy-activity) (with description of experimental setup) - Flare spectroscopy research: [http://publiclab.org/tag/flare](http://publiclab.org/tag/flare) - A report from user [straylight](/profile/straylight) on a classroom activity involving [measuring different elements in a bunsen burner flame](/notes/straylight/10-14-2012/classroom-flame-spectroscopy) - A listing of imported emission spectra of elements from the NIST database so far: [https://spectralworkbench.org/tag/nist](https://spectralworkbench.org/tag/nist) --------- ### Activities [activities:spectrometry-sampling]...

Author Comment Last activity Moderation
Fernmoss "Can a 405 nm led be used to visualize heating oil stains? " | Read more » over 2 years ago
laxmiassociates "Very informative. Information is detailed in a comprehensive way regarding oil testing. Insightful. Thank you for this. " | Read more » over 3 years ago
Ag8n " The kits for these tests ( someone correct me if I'm wrong) appear to be made by RenekaBio. A quick look down the test procedure and method showe..." | Read more » over 5 years ago
bararesbest " What is the solution 2? " | Read more » over 5 years ago
springem "Hi, new user here. Just got word from my water company that their turbidometer has been going offline for a few months. I'm curious if you have upl..." | Read more » about 6 years ago
programmer1200 "Here is a link to the source but its cheaper to purchase at the actual store , for some reason they $1.71 website and only a $1 in store . https:/..." | Read more » about 6 years ago
warren "Also, do you have a link to the light you used? Do you use a diffuser of any kind with it, or could you in theory dim the light with a filter to ma..." | Read more » about 6 years ago
warren "That sounds amazing. Looking forward to seeing it! " | Read more » about 6 years ago
programmer1200 "Hi @warren that sounds great I'll get one printed out and ready for use and should have it on its way within a few days. Your right about the stand..." | Read more » about 6 years ago
warren "Hi, this is tremendous, we'd love one at the Kits initiative! Could we trade you for some Lego parts? We're curious if you'd be interested in using..." | Read more » about 6 years ago
briandegger "Great article. Its also good to know about Renekabio(based in US and Indonesia ftw) and their set of assays. Is this the detection kit you used? h..." | Read more » about 6 years ago
neilh20 "Very interesting. A new board from seeed is intriguing- though a bit pricey - seems like it could be turned into an auto-monitoring system. https:/..." | Read more » almost 7 years ago
dhaffnersr "It's me again Jeff, Dave H, sorry I posted the wrong graph i made, this is the right one " | Read more » about 8 years ago
dhaffnersr "Hey Jeff, I use spekwin32 for all my spectral data processing, first here are 2 references that may help you https://www.researchgate.net/topic/uv..." | Read more » about 8 years ago
warren "Hi, Dave - what is the tell-tale hump? Do you mean from the LED input light? If so, it's at 398nm, not 385nm. What processing did you do? " | Read more » about 8 years ago
dhaffnersr "Hey Jeff, I saw your spectra of the nail polish machine and there it is the tell tail "hump," so I exported it and processed it and here is what it..." | Read more » about 8 years ago
dhaffnersr "Hey Dave, well I was thinking along the lines of when I built a wind speed indicator with a small dc motor and LCD screen attached and calibrated i..." | Read more » about 8 years ago
stoft "Unfortunately, LED wavelength does not change with applied voltage or current -- their center peak wavelength is not variable or controllable and P..." | Read more » about 8 years ago
dhaffnersr "Hey Jeff! Sure I'd be happy to test any LEDs you want to send. I do want to throw an idea your way, I think using the higher wavelength LEDs are st..." | Read more » about 8 years ago
stoft "Sure ... what's the LED's packaging style/type? SMD, leaded, ...? " | Read more » about 8 years ago
warren "@dhaffnersr and @stoft, if you'd like I could send you the lower-wavelength LEDs as well for comparison testing? " | Read more » about 8 years ago
warren "@briandegger @jeffh - thanks for the tips on LED sourcing! Thought you'd enjoy seeing this. " | Read more » about 8 years ago
straylight "thanks ygzstc, that makes sense. I think that the approximation that relative intensity measured from the scope can be used in place of the log rel..." | Read more » about 8 years ago
ygzstc "Yes the Beer-Lambert Law is based on -log(I/Io) but it's applicable for a single wavelength value. (https://en.wikipedia.org/wiki/Beer%E2%80%93Lamb..." | Read more » about 8 years ago