Identifying recent cannabis intake is confounded by prolonged cannabinoid excretion in chronic frequent cannabis users. We previously observed detection times ≤2.1 h for cannabidiol (CBD) and cannabinol (CBN) and 9-tetrahydrocannabinol (THC)-glucuronide in whole blood after smoking, suggesting their applicability for identifying recent intake. However, whole blood collection may not occur for up to 4 h during driving under the influence of drugs investigations, making a recent-use marker with a 6–8 h detection window helpful for improving whole blood cannabinoid interpretation. Other minor cannabinoids cannabigerol (CBG), 9-tetrahydrocannabivarin (THCV), and its metabolite 11-nor-9-
carboxy-THCV (THCVCOOH) might also be useful. We developed and validated a sensitive and specific
liquid chromatography-tandem mass spectrometry method for quantification of THC, its phase I and
glucuronide phase II metabolites, and 5 five minor cannabinoids. Cannabinoids were extracted from
200 L whole blood via disposable pipette extraction, separated on a C18 column, and detected via electrospray ionization in negative mode with scheduled multiple reaction mass spectrometric monitoring.
Linear ranges were 0.5–100 g/L for THC and 11-nor-9-carboxy-THC (THCCOOH); 0.5–50 g/L for 11-
hydroxy-THC (11-OH-THC), CBD, CBN, and THC-glucuronide; 1–50 g/L for CBG, THCV, and THCVCOOH; and 5–500 g/L for THCCOOH-glucuronide. Inter-day accuracy and precision at low, mid and high quality control (QC) concentrations were 95.1-113% and 2.4-8.5%, respectively (n = 25). Extraction recoveries and matrix effects at low and high QC concentrations were 54.0-84.4% and −25.8-30.6%, respectively.
By simultaneously monitoring multiple cannabinoids and metabolites, identification of recent cannabis administration or discrimination between licit medicinal and illicit recreational cannabis use can be improved.