Chromophoric labeling of cannabinoids with 4-dimethylaminoazobenzene-4'-sulfonyl chloride.

A simple and sensitive assay for the cannabinoids is presented using a dabsylation procedure. Dabsyl derivatives of delta 9-tetrahydrocannabinol (delta 9-THC) and cannabinol (CBN) were prepared by reacting with 4-dimethylaminoazobenzene-4'-sulfonyl chloride (dabsyl chloride) in acetone in the presence of sodium carbonate-sodium bicarbonate buffer (pH 10). Crystalline dabsylcannabinoids gave intense absorption in the visible region. With these derivatives, analysis by thin-layer chromatography (TLC) and high performance liquid chromatography (HPLC) were tested. These techniques gave good separation and nanogram detection of dabsyl-THC and -CBN by using n-hexane-ethyl acetate-diethylamine (20:5:1) for TLC and MeOH--H2O (95:5) at 450 nm for HPLC.