Analysis of the major metabolite of delta 9-tetrahydrocannabinol in urine. IV. A comparison of five methods

Urinary cannabinoid analysis: comparison of four immunoassays with gas chromatography-mass spectrometry

Eight-eight urine samples were analysed by the EMIT d.a.u. Cannabinoid 20 ng homogeneous enzyme immunoassay, the DPC cannabinoid radioimmunoassay, two in-house cannabinoid radioimmunoassays and a gas chromatography-mass spectrometry method for 11-nor-9-carboxy-delta 9-tetrahydrocannabinol. There was good qualitative agreement between the methods with few discrepancies in the borderline region.

Correlations on radioimmunoassay, fluorescence polarization immunoassay, and enzyme immunoassay of cannabis metabolites with gas chromatography/mass spectrometry analysis of 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid in urine specimens

Results obtained from three commercial immunoassay kits, Abuscreen, TDx, and EMIT, commonly used for the initial test of urine cannabinoids (and metabolites) were correlated with the 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (9-THC-COOH) concentration as determined by GC/MS. Correlation coefficients obtained based on 26 (out of 1359 total sample population) highly relevant samples, are 0.601 and 0.438 for Abuscreen and TDx. Correlation coefficients obtained from a parallel study on a different set of 47 (out of 5070 total sample population) highly relevant specimens are 0.658 and 0.575 for Abuscreen and Emit. The immunoassay concentration levels, that correspond to the commonly used 15 ng/ml GC/MS cutoff value for 9-THC-COOH, as calculated from the regression equations are 82 ng/ml and 75 ng/ml for TDx and EMIT and 120 ng/ml and 72 ng/ml for Abuscreen manufactured at two different time periods. The difference of these calculated corresponding concentrations provides quantitative evidence of the reagent specificity differences.

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-delta 9-tetrahydrocannabinol (delta 9-THC-COOH) in blood and urine samples found to be positive by two in-house cannabinoid radioimmunoassays (RIAs). The delta 9-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.

Optimization of the quantitative analysis of the major cannabis metabolite (11-nor-9-COOH-delta 9-tetrahydrocannabinol) in urine by gas chromatography/mass spectrometry

A gas chromatographic/mass spectrometric electron impact method is presented for the detection and quantification of 11-nor-9-carboxy-delta 9-tetrahydrocannabinol (THC-COOH) in urine, for use in the confirmation of presumptive results obtained by other techniques. Four extraction procedures, two solid-liquid and two liquid-liquid, have been compared. A comparison of two trimethylsilylating methods demonstrates that the best results are obtained by the use of a mixture containing N-methyl-N-trimethylsilyl-trifluoroacetamide, trimethyliodosilane and dithioerithritol (100:0.2:1) v/v/w. The use of ketoprofen as a new internal standard for the quantification of THC-COOH has proved to be very effective. Both spiked samples and samples from cannabis users have been successfully analysed. It has also been demonstrated that the presence of other drugs of abuse in urine samples do not interfere with cannabis quantification by the method reported here.

Monitoring urine for inhaled cannabinoids

The current position on the "passive smoking" of cannabis is reviewed with particular reference to the analysis of urine. The pharmacokinetics and metabolism of delta-9-tetrahydrocannabinol are first described, followed by a survey of methods used to identify and quantify its metabolites in urine. Published data concerning the appearance of cannabinoids in urine following "passive smoking" of cannabis are compared and the most important factors described. The problems of interpreting the results of the analysis of urine in forensic cases are discussed and a possible means to clarify the position by means of analysing serum is suggested.