Optimization of recombinant β-glucuronidase hydrolysis and quantification of eight urinary cannabinoids and metabolites by liquid chromatography tandem mass spectrometry

Abstract

Prolonged urinary cannabinoid excretion in chronic frequent cannabis users confounds identification of recent cannabis intake that may be important in treatment, workplace, clinical, and forensic testing programs. In addition, differentiation of synthetic Δ9-tetrahydrocannabinol (THC) intake from cannabis plant products might be an important interpretive issue. THC, 11-hydroxy-THC (11-OH-THC) and 11-nor-9-carboxy-THC (THCCOOH) urine concentrations were evaluated during previous controlled cannabis administration studies following tandem alkaline/E. coli β-glucuronidase hydrolysis. We optimized recombinant β-glucuronidase enzymatic urinary hydrolysis before simultaneous liquid chromatography tandem mass spectrometry (LC-MS/MS) quantification of THC, 11-OH-THC, THCCOOH, cannabidiol (CBD), cannabinol (CBN), cannabigerol (CBG), tetrahydrocannabivarin (THCV) and 11-nor-9-carboxy-THCV (THCVCOOH) in urine. Enzyme amount, incubation time and temperature, buffer molarity and pH were optimized using pooled urine samples collected during a National Institute on Drug Abuse, Institutional Review Board-approved clinical study. Optimized cannabinoid hydrolysis with recombinant β-glucuronidase was achieved with 2000 IU enzyme, 2 M pH 6.8 sodium phosphate buffer, and 0.2 mL urine at 37°C for 16 h. The LC-MS/MS quantification method for hydrolyzed urinary cannabinoids was validated per the Scientific Working Group on Toxicology guidelines. Linear ranges were 1-250 μg/L for THC and CBG, 2-250 μg/L for 11-OH-THC, CBD, CBN, THCV and THCVCOOH, and 1-500 μg/L for THCCOOH. Inter-batch analytical bias was 92.4-112.4%, imprecision 4.4-9.3% CV (n = 25), extraction efficiency 44.3-97.1% and matrix effect -29.6 to 1.8% (n = 10). The method was utilized to analyze urine specimens collected during our controlled smoked, vaporized, and edible cannabis administration study to improve interpretation of urine cannabinoid test results.

Keywords: LC-MS/MS; cannabinoids; urine; β-glucuronidase.