Cannabinoids in humans. I. Analysis of delta 9-tetrahydrocannabinol and six metabolites in plasma and urine using GC-MS.

This report describes a method for the quantitative analysis of delta 9-tetrahydrocannabinol and six of its metabolites, 8 alpha-hydroxy-delta 9-tetrahydrocannabinol, 8 beta-hydroxy-delta 9-tetrahydrocannabinol, 11-hydroxy-delta 9-tetrahydrocannabinol, 8 alpha,11-dihydroxy-delta 9-tetrahydrocannabinol, 8 beta,11-dihydroxy-delta 9-tetrahydrocannabinol, and 11-nor-9-carboxy-delta 9-tetrahydrocannabinol. In addition, the method was designed to detect cannabidiol and cannabinol, two naturally occurring cannabinoids. Plasma and urine samples were hydrolyzed with bacterial (Escherichia coli) beta-glucuronidase and extracted with hexane-ethyl acetate (7:1). Analysis and quantitation were performed by gas chromatography-mass spectrometry in the electron ionization mode coupled with selected ion monitoring. The cannabinoids were detected as their trimethylsilyl derivatives to enhance their chromatographic separation and mass spectral characteristics. The linearity of the procedure was excellent for all of the compounds within the range tested (0-100 ng/mL). Limits of detection ranged from 0.5 to 1.5 ng/mL in urine and from 0.6 to 2.1 ng/mL in plasma depending on the analyte.