Method for postmortem tissue quantification of Δ9-tetrahydrocannabinol and metabolites using LC–MS-MS

Abstract

A method for analyzing Δ9-tetrahydrocannabinol (THC), 11-hydroxy-Δ9-THC (THC-OH) and 11-nor-Δ9-THC-9-carboxylic acid (THC-COOH) in postmortem solid specimens using liquid chromatography–tandem mass spectrometry was developed and validated. A Stomacher instrument was used to prepare these tissues before extraction. Prior to solid phase extraction, liver, kidney, stomach, lung, brain, muscle, bladder and intestine tissues were pretreated with alkaline hydrolysis. All calibration curves were found to be linear with coefficients of determination greater than 0.99. The limit of quantification was 1.0 ng/g. Using three controls, within-run precision ranged between 1.0 and 12.0%, between-run precision ranged between 1.0 and 6.0%, and accuracy ranged between −7.0 and 8.0%. Matrix effects ranged from −21 to 24%. After matrix effects were excluded, analytical recoveries ranged from 79 to 97%. The distributions of THC, THC-OH and THC-COOH were investigated in 32 postmortem cases that tested positive for cannabinoids. This revealed new information regarding the distribution of THC metabolites in stomach, intestine and bladder. Alkaline hydrolysis was sufficient for the deglucuronidation of THC-COOH-glucuronide to its free form, THC-COOH, in all tissues of interest. In conclusion, measuring THC and its metabolites (THC-OH and THC-COOH) in tissues is crucial for any forensic toxicology detection method, especially when bodies are heavily decomposed, as solid tissues may be the only specimens available for testing.