GAS-CHROMATOGRAPHIC MASS-SPECTROMETRIC CONFIRMATION OF RADIOIMMUNOASSAY RESULTS FOR CANNABINOIDS IN BLOOD AND URINE

A simple gas chromatographic-mass spectrometric (GC-MS) method is described for the detection of 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (Δ9-THC-COOH) in blood and urine samples found to be positive by two in-house cannabinoid radioimmunoassays (RIAs). The Δ9-THC-COOH in the samples, which is partly present as its glucuronide conjugate, is isolated by solvent extraction after hydrolysis of the glucuronide. It is converted to its trimethylsilyl derivative and analysed by capillary GC-MS in the electron impact mode with selected ion recording. All samples that were positive by both RIAs were also positive by GC-MS apart from four blood and two urine samples in which the GC-MS results were inconclusive owing to the presence of coextractives. No sample that was positive by both RIAs was found to be negative by GC-MS. © 1990.