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Kava Science Practical considerations for an inexpensive field instrument for UV kava testing

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HeadHodge said:
Could you give us the digest (for Dummies) version here?
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In the method described here:
http://www.sciencedirect.com/science/article/pii/S0889157517300443
They figured out that you can determine the ratio of kavain to DHM in kava extract by measuring the ratio of the absorbances of ultraviolet light of two different wavelengths: 250 nm and 290 nm. "Absorbance" means how much light is absorbed at a specific wavelength, and is proportional to the concentration of chemicals in the sample. They showed that this ratio can distinguish between noble, tudei and wiichmannii varieties of kava with good accuracy. Those wavelengths are deep in the ultraviolet, so I discuss some possible light sources that could be used, and detectors that work at those wavelengths, and other stuff to make a simple instrument that could be used to do this test. I describe three versions of the instrument, in increasing order of how accurately they should be able to do the method: "Economy", "Midline" and "Deluxe". I estimate the parts for each of these would cost USD 250, 500 or 1100, respectively.
 
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Deleted User said:
In addition to the instrument you would also need the items below, prices are minimums:
  • UV compatible cuvettes ($70 per 100)
  • UV/HPLC grade diethyl ether ($65/L including Hazmat fees)
  • sonicator ($85, Harbor Freight)
  • centrifuge ($150, ebay)
  • scale ($50, but I doubt the repeatability of these!)
  • misc lab supplies (prep tubes, pipettes, etc, ~$150)
The method calls for a 100:1 dilution, so cost per test would depend on how fancy a pipetting system you use. I'd estimate about $5 per test average.

For calibration you could use a holmium filter ($139)
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yup. You could actually do without the sonicator and centrifuge if you are willing to let the samples settle over night. There is also the possibility the method could work with methanol (or ethanol) instead of ether. In the paper they found that ether was optimal, but methanol might be OK, and is easier to get. (Acetone doesn't work because it does not transmit uv at those wavelengths)
 
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The holmium filter wouldn't work or be necessary for the mercury lamps, because those have very narrow lines, and this instrument would not collect a complete spectrum, so you couldn't see the peaks in the holmium filter. Mercury lamps themselves are actually used to calibrate things.

Another thing to note is that because the method uses a ratio of absorbances, it would not be very sensitive to concentration, so a cheap scale would probably be fine.

Of course the more money you spend, the more accurate a result you could get. But the question I am wondering about is: is it possible to get something useful on the cheap.
 
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