DIY Spectrometer and CBD/THC analysis: Results

In an earlier, lengthy post I described my spectrometer build and showed the spectrum from a CFL lamp.  Since then, I have continued with experiments to see if the dye (Fast Blue B) could be used to produce more quantitative data on CBD and THC content.

My executive summary:  the color shift between CBD and THC is too subtle to use as an analytical tool.

Below, I show two spectrograms -- taken with extracts from two different marijuana clones.  One contains less than 1% THC and one contains no CBD, as determined by my wet chemical analysis (a 5% sodium hydroxide solution in ethyl alcohol turns blue if CBD is present).  The differences are very subtle, making it very difficult to distinguish between the two.

So in conclusion, I made a fairly nice spectrometer I can use for other things, but my primary goal -- being able to determine the relative amounts of CBD and THC in plant material -- was not achieved using this approach.