An automated and simultaneous solid-phase extraction of Δ9-tetrahydrocannabinol and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol from whole blood using the Zmark RapidTrace™ with confirmation and quantitation by GC-El-MS

A sensitive, reliable, and automated solid-phase extraction (SPE) method was developed for the simultaneous extraction, confirmation, and quantitation of Δ9-tetrahydrocannabinol (THC) and 11-nor-9-carboxy-Δ9- tetrahydrocannabinol (THCCOOH) from whole blood. The extraction was performed on the Zymark RapidTrace SPE Workstation with a reduced solvent volume SPE copolymer cartridge. Quantitative analysis was completed on a benchtop gas chromatograph-mass spectrometer using electron ionization mode with selected ion monitoring of three ions for each analyte. The limits of quantitation for THC and THCCOOH were 2 ng/mL and 1 ng/mL, respectively. The limits of detection for THC and THCCOOH were 1.6 ng/mL and 0.8 ng/mL, respectively. Extensive method validation is presented including extraction recoveries, within-run precision, day-to-day precision, linearity, and carryover. This procedure is used routinely in the laboratory on blood samples screened positive for cannabinoids.