New extraction method of THC and its metabolites, 11-OH-THC and THC-COOH, in plasma

Objectives: A liquid/liquid extraction technique on solid support of Δ9-tetradydrocannabinol (THC), 11-hydroxy-Δ9-tetradydrocannabinol (11-OH-THC) and 11-nor-Δ9-tetradydrocannabinol-9-carboxylic acid (THCCOOH) in plasma was developed in order to be assayed by high-performance liquid chromatography and tandem mass spectrometry (HPLC-MS/MS). Methods: The samples were extracted by liquid/liquid extraction over solid support of an extraction cartridge. The extracts were thereafter dried down and injected into the HPLC-MS/MS system set with a positive electrospray mode using a Waters XTerra MS C18 3.5-μm 2.1 × 150 mm column. Results: The extraction recovery levels were 66%, 70% and 71% for THC, and 75%, 93% and 101% for 11-OH-THC at concentrations of 2.5, 5 and 10 ng/mL, respectively. They were 86% and 78% for THC-COOH at concentrations of 5 and 10 ng/mL. The limits of detection (LOD) were 0.09, 0.08 and 0.91 ng/mL for THC, 11-OH-THC and THC-COOH, respectively. The limits of quantification (LOQ) were 0.16, 0.15 and 3.24 ng/mL for THC, 11-OH-THC and THC-COOH, respectively. The inter-series incertitude CV determined for concentrations of 1, 2.5 and 10 ng/mL were 12.1%, 12.0% and 6.4% for THC, 14.5%, 11.1% and 7.2% for 11-OH-THC, and 14.9%, 26.2% and 11.3% for THC-COOH. Conclusion: The novel extraction method for THC, 11-OH-THC and THC-COOH developed in this work is rapid, sensitive and specific. It may be a valuable tool for predictive toxicology, high-throughput metabolism and pharmacokinetic studies of cannabinoids.