The determination of Δ9-tetrahydrocannabinol and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol in whole blood using solvent extraction combined with polar solid-phase extraction

A method for the determination of Δ9-tetrahydrocannabinol (THC) and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH) in whole blood using conventional solvent extraction followed by a cleanup using polar solid-phase cartridges is described. The method uses 0.5 mL of blood, and detection is by benchtop gas chromatography-mass selective detection using selected ion monitoring. The limit of detection is better than 1 ng/mL, and extraction efficiencies are greater than 80% for THC and 70% for THCCOOH. The method is robust and highly reproducible.