Testing for THC and CBD Content

At the present time there seems to be no good color test which reacts only with THC. However, if the Beam test is first run and shows the presence of relatively little CBD, many different tests can then be applied to the marijuana to roughly quantitate the THC content by first subtracting the value of the 

Beam test. One of the easiest of these is the Duquenois test. Prepare an extract as above and evaporate it to dryness. Add four drops Duquenois reagent (0.4 g vanillin, five drops acetaldehyde in 20 ml 95% ethanol), then eight drops concentrated HCl, mix and let stand ten minutes. The violet color can be compared against standards of known THC content as above. If the color is too intense, use less sample or less extract and vice versa. 

Samples can be sent to labs for quantitative analyses, but you will have to go through some paperwork and hassles so you may prefer to roughly quantitate the test by analyzing marijuana you have already smoked. 

Many tests give different colors with CBD, CBN and THC, and these might be used to measure CBD and THC simultaneously, especially if a colorimeter is available.  

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