This article reports for the first time a miniaturized reaction directly on a 3.5 mm diameter solid substrate of a material previously developed in the authors’ laboratory using a methanol extract from ∼10 mg of plant sample.
The Fast Blue BB (FBBB) colorimetric test has been shown to differentiate between the different cannabinoids found in cannabis addressing the urgent need to distinguish between hemp-type cannabis, which is legal in every state of the US, from marijuana-type cannabis (≥0.3% w/w THC). FBBB forms a red chromophore in the presence of THC, an orange chromophore in the presence of CBD, a detectable fluorophore with THC but no fluorescence with CBD. In the current study, various cannabinoids, various herbs and spices, and authentic cannabis samples were tested with the optimized color test, and the FBBB reaction was found selective for THC relative to other cannabinoids and herbs and spices. RGB (Red, Green, Blue) numerical codes were obtained for each color (and fluorescence) image produced by the reaction. Linear Discriminant Analysis (LDA) results correctly classify a set of 25 known plant samples (marijuana, hemp and herbs and spices) as either containing THC levels below 0.3% (w/w) (hemp) or as containing high THC levels (≥0.3% w/w) and low CBD levels (marijuana). Cannabis samples containing low THC (but just above 0.3%) and high CBD (THC:CBD ratios <2) were incorrectly classified, however. None of the herbs or spices tested were incorrectly classified as either hemp or marijuana. (Publisher abstract)