Identification and quantification of cannabinoids in postmortem fluids and tissues by liquid chromatography-tandem mass spectrometry

Cannabis sativa is commonly used worldwide and is frequently detected by forensic laboratories working with biological specimens from potentially impaired drivers or pilots. To address the problem of limited published methods for cannabinoids quantification in postmortem specimens, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated to quantify Δ⁹–tetrahydrocannabinol (THC), 11-hydroxy-THC (11-OH-THC), 11-nor-9-carboxy-THC (THCCOOH), 8β,11-dihydroxy-THC (8β-diOH-THC), 8β-hydroxy-THC (8β-OH-THC), THC-glucuronide (THC-g), THCCOOH-glucuronide (THCCOOH-g), cannabidiol (CBD), cannabinol (CBN), cannabigerol (CBG), Δ⁹-tetrahydrocannabivarin (THCV), and 11-nor-9-carboxy-THCV (THCVCOOH). Solid phase extraction concentrated analytes prior to analysis on a biphenyl column coupled to a mass spectrometer in electrospray positive ionization mode using multiple reaction monitoring. Linearity ranged from 0.25-50 ng/mL (THC-g), 0.5-100 ng/mL (CBN), 0.5-250 ng/mL (THC, 11-OH-THC, THCCOOH, CBD, and CBG), 1-100 ng/mL (8β-diOH-THC, THCVCOOH, 8β-OH-THC, and THCV) and 1-250 ng/mL (THCCOOH-g). Within-run imprecision was <11.2% CV, between-run imprecision <18.1% CV, and bias was less than ±15.1% of target concentration in blood for all cannabinoids at three concentrations. No carryover or interferences were observed. All cannabinoids were stable in blood at room temperature for 24 h, refrigerated (4°C) for 96 h, and following three freeze/thaw cycles. Matrix effects greater than 25% were observed for most analytes in tissues. The proof of concept for method applicability involved measurement of cannabinoids in a pilot fatally injured in an aviation crash. This new analytical method is robust and sensitive, enabling collection of additional cannabinoid postmortem distribution data to improve interpretation of postmortem cannabinoid results.