Enhancement and validation of a quantitative GC–MS method for the detection of ∆9-THC and THC COOH in postmortem blood and urine samples

Cannabis is frequently detected in forensic investigations and is associated with an increased risk of fatal car crashes. This study aims to develop a method to detect and measure ∆9-tetrahydrocannabinol (∆9-THC) in blood and its metabolite, 11-nor-9-tetrahydrocannabinol-carboxylic acid (∆9-THC-COOH), in urine. The procedure employs two liquid-liquid extraction methods in conjunction with GC-MS in SIM mode. Both compounds were successfully processed, demonstrating the method's ease of use and efficiency. The method was validated for selectivity, identification capability, linearity, precision, limit of detection (LOD), limit of quantification (LOQ), and accuracy. Its effectiveness was further demonstrated by applying it to 30 authentic urine and blood samples from cannabis-related cases, establishing it as a valuable option for routine cannabinoid analysis in forensic toxicology labs.•The linearity range was 25-300 ng/mL for ∆9-THC in blood, and 50-300 ng/mL for ∆9-THC-COOH in urine, and calibration curves for both analytes showed R² values consistently above 0.989, confirming their linearity.•The LOD and LOQ for THC-COOH in hydrolyzed urine were 25 ng/mL and 50 ng/mL, respectively, and for THC in blood, they were 15 ng/mL and 25 ng/mL, respectively.•The variation coefficients were below 14%, and recoveries exceeded 81% for both compounds.