Development and validation of a method for the quantitation of Δ9tetrahydrocannabinol in oral fluid by liquid chromatography electrospray–mass-spectrometry

Analysis of Δ9tetrahydrocannabinol (Δ9THC) and its metabolites in biological samples is of great relevance for forensic purposes. In the case of oral fluid (OF), the analysis should determine Δ9THC, whereas in urine, it detects the inactive metabolite tetrahydrocannabinol carboxylic acid (THC-COOH). Most laboratories analyze Δ9THC in such samples using GC–MS methods, but these procedures are time-consuming and involve unavoidable previous extraction and derivatization. No data is yet available on the application of liquid chromatography–mass-spectrometry to detect Δ9THC in oral fluid. We report a validation method in which the Δ9THC is isolated from oral fluid by a simple liquid–liquid extraction with hexane and subsequently analyzed by liquid chromatography–mass-spectrometry. thod here reported for the determination of Δ9THC in oral fluid only requires 200 μl of sample and achieves limits of detection of 2 ng/ml, and has been used to analyze oral fluid samples collected from current drug users.