Home-brew Cannabis potency analysis

Last year, due to an issue with improperly-marked marijuana plants, we ended up with some plants that had zero CBD content.  We are interested in the pain management properties of CBD, not getting high, so last year was a waste of our gardening time, water and garden space.  It was when I started looking into ways of doing my own analysis.  Sending material to a lab is expensive, particularly if you want to test a number of times to optimize your THC/CBD ratio (which depends on the "ripeness" of the buds).  My results, if successful, also could be helpful to others who are depending on getting the right "stuff" for their needs.

I started by looking at current mainstream methods.  Mainstream analysis techniques fall into several categories:  Gas chromatography, liquid chromatography, mass spectroscopy, and IR spectroscopy.  Thin Layer Chromatography kits can be purchased for home use, but they're not very good for quantitative work -- the size of a particular colored blob on the TLC plate is roughly proportional to the amount of chemical (THC, CBD etc.), but in my experience it was difficult to interpret the streaks on the plate.

While mulling over all these approaches, I did find a purely chemical way to at least tell you if your marijuana has some CBD in it.  It's pretty simple, too:  make up a 5% (by weight) solution of sodium hydroxide (A.K.A. lye) in ethanol or rubbing alcohol.    Put 100-200 milligrams of your decarbed bud in a glass vial and add the solution  at least halfway up the vial.  Screw on the cap and shake vigorously.  If the solution turns blue, your marijuana contains CBD.  The darker the color, the more CBD you've got.  THC doesn't turn blue.  With careful solution preparation and careful weighing it might be possible to get a quantitative measure of the CBD, but you'd need a spectrometer to tell you what the absorptivity of the solution is.  You can make a spectrometer using a web cam and DVD (for the diffraction grating).

I also discovered a paper that has a lot of information on cannabinoid analysis.  Its title:  "Chromatographic and Spectroscopic Data of Cannabinoids from Cannabis sativa L.", by Arno Hazekamp, Anja Peltenburg and Rob Verpoorte.  It turns out decarbed cannabinoids have a distinctive red fluorescence when illuminated by UV.  This may be the basis of a commercial THC analysis gadget that is currently selling for around $300 (pure speculation on my part).  The photo below shows three different samples I examined.  Two are decarbed bud and one is UN-decarbed.  Hexane is used as the solvent.

Pretty interesting.  While not shown, I also observed the same fluorescence in cannaoil made with coconut oil.  It glows a very pretty orange color, while pure coconut oil just reflects the purple color of the UV flashlight.  Cannaoil made with un-decarbed cannabis also doesn't glow orange.  The flashlight's peak output is specified to be at 390 nm.

The fact that the decarbed cannabinoids fluoresce suggests the mechanism is related to the site where the carboxyl group was (formerly) attached.  It's a benzene ring structure with an OH attached so technically speaking it's a phenol.  It would be nice if CBD fluoresced with a different color but at least the effect can be useful for a total cannabinoid test.

Searching the web, I found a thread on a MJ forum where the poster had noted the same thing.  The post mentioned some variability in the effect, comparing a commercial extract to a home-brew version.  I suspect the starting materials were different -- one was decarbed, the other, not.  There was speculation that the fluorescence was from chlorophyll, but as can be seen in my photo above, a chlorophyll-loaded UNdecarbed sample doesn't glow orange.  It's the vial on the right.