Quantitative analysis of tetrahydrocannabinol isomers and other toxicologically relevant drugs in blood

Abstract

AbstractA multi‐analyte liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) method is described, involving the separation of delta‐9‐tetrahydrocannabinol (delta‐9‐THC) and delta‐8‐THC in addition to other commonly encountered drugs and metabolites. Briefly, sample preparation involved an alkaline liquid–liquid extraction (methyl tert‐butyl ether) of blood (100 μl). The solvent layer was transferred, evaporated to dryness, reconstituted, and samples then separated on an Agilent Poroshell 120 EC‐C18 100 Å (50 mm × 3.0 mm, 2.7 μm) analytical column using a multi‐step gradient elution of 50 mM ammonium formate in water (pH 3.5) and 0.1% formic acid in methanol over 14 min. A SCIEX Triple Quad 6500+ system operating in scheduled multiple reaction monitoring and positive electrospray ionization was used for detection. There were no interferences, and matrix effects were generally acceptable (±20% of neat response). Linearity was achieved within the calibration range, including methylamphetamine (MA) (10–1000 ng/ml), 3,4‐methylenedioxy‐N‐methylamphetamine (MDMA) (10–1,000 ng/ml), cocaine (10–1000 ng/ml), and two THC isomers (1–100 ng/ml). Accuracies of MA, MDMA, cocaine, and two THC isomers were 3.6 to 8.9%, −1.2 to 4%, −5.3 to 5.8%, and −11 to 14%, respectively; while precision estimates of the same were 1.6 to 5.4%, 1.7 to 5.3%, 1.2 to 4.5%, and 2 to 10%, respectively. Autosampler stability and dilution integrity were within acceptable limits, and no carryover was detected at the limit of detection. This validated LC‐MS/MS method made the routine identification of both delta‐9‐THC and delta‐8‐THC in blood possible.