This paper reports on a research study that focuses on the ability to quantitate Δ9-THC in a sample using the fluorescence of the THC+Fast Blue BB complex, observed with a portable fluorescence reader to gather objective data that may be related to Δ9-THC concentration; the paper also introduces a portable colorimeter that can improve both the 4-AP and the FBBB color test evaluation by reducing subjectivity.
The Fast Blue BB (FBBB) and 4-aminophenol (4-AP) colorimetric tests have been reportedly used for the qualitative determination of Δ9-THC in plants and for the differentiation between marijuana and hemp-type cannabis. The authors report the miniaturization of the FBBB colorimetric reaction on a silicone treated filter paper substrate and the analytical figures of merit for a quantitative determination of Δ9-THC for the first time. The reaction between Δ9-THC and FBBB forms a red chromophore that fluoresces when irradiated with visible (480 nm) or UV (365 nm) light, providing a 3-fold increase in sensitivity. Portable instruments are introduced for the objective color determination for both tests and for the fluorescence reading of the THC + FBBB complex. The authors report a fluorescence signal with Δ9-THC, Δ8-THC, and CBN. The limit of detection (LOD) was determined to be 1.6 ng/μL with precision ∼12 percent RSD for standard Δ9-THC solutions ranging between 5 and 20 ng/μL. The linear dynamic range for this test is reported between 1.6 ng/μL and 20 ng/μL for the portable fluorescence detector. The miniaturization of both colorimetric tests and the increased sensitivity of the FBBB test using fluorescence analysis, coupled to portable instruments allows for limited quantitative analysis of cannabis plants in the field. (Published Abstract Provided)