Analysis of 11-nor-Δ9-tetrahydrocannabinol-9-carboxylic acid and its glucuronide in urine by capillary electrophoresis/mass spectrometry

Δ9-Tetrahydrocannabinol is the primary psychoactive component in cannabis, one of the most commonly used illicit drugs in the world. This paper describes a simple and rapid method for direct analysis of major metabolites of Δ9-tetrahydrocannabinol; 11-nor-Δ9-tetrahydrocannabinol-9-carboxylic acid and its glucuronide in urine by capillary electrophoresis/mass spectrometry. The only pretreatment needed for a urine sample was dilution with methanol containing an internal standard and centrifugation. Electrophoresis was carried out in an untreated fused-silica capillary (50 µm i.d. × 85 cm) filled with 40 m m ammonium formate (pH 6.4). An analysis could be completed within 10 min. For both compounds, the assay was linear over the range 0.1 − 10 µg/mL in urine with correlation coefficients (r2) > 0.99 and the limit of detection was 0.5 pg (10 nL injection). The detection yields and reproducibilities were determined at three different concentrations (0.1, 0.5 and 2 µg/mL in urine). The mean detection yields were 60 − 99%. The intra- and inter-day relative standard deviations of migration times were 0.063 − 0.19 and 0.18 − 0.36%, and those of peak areas were 4.2 − 18 and 5.9 − 25%, respectively. The proposed method successfully analyzed the urine samples of cannabis users. Copyright © 2012 John Wiley & Sons, Ltd.