A novel fast method for aqueous derivatization of THC, OH-THC and THC-COOH in human whole blood and urine samples for routine forensic analyses.

A novel aqueous in situ derivatization procedure with propyl chloroformate (PCF) for the simultaneous, quantitative analysis of Δ9-tetrahydrocannabinol (THC), 11-hydroxy-Δ9-tetrahydrocannabinol (OH-THC) and 11-nor-Δ9-tetrahydrocannabinol-carboxylic acid (THC-COOH) in human blood and urine is proposed. Unlike current methods based on the silylating agent (BSTFA) added in an anhydrous environment, this new proposed method allows to add the derivatizing agent (propyl chloroformate, PCF) directly to the deproteinized blood and recover the derivatives by liquid-liquid extraction. This novel method can be also used for hydrolyzed urine samples, which is faster than the traditional method involving a derivatization with trimethyloxonium tetrafluoroborate (TMO). The analytes are separated, detected and quantified by gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring mode (SIM). The method was validated in terms of selectivity, capacity of identification, limits of detection (LOD) and quantification (LOQ), carryover, linearity, intra-assay precision, inter-assay precision and accuracy. The limits of detection (LOD) and quantification (LOQ) in hydrolyzed urine were 0.5 ng/mL and 1.3 ng/mL for THC and 1.2 ng/mL and 2.6 ng/mL for THC-COOH, respectively. In blood, the LOD and LOQ were 0.2 ng/mL and 0.5 ng/mL for THC, 0.2 ng/mL and 0.6 ng/mL for OH-THC, 0.9 ng/mL and 2.4 ng/mL for THC-COOH, respectively. This method was applied to thirty-five urine samples and fifty blood samples resulting to be equivalent to the current ones with the advantage of a more simple and faster sample processing time. We believe it will be a more convenient option for the routine analysis of cannabinoids in toxicological and forensic laboratories.