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

Urine samples from 29 subjects were simultaneously analyzed for 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid by five previously published methods. The procedures employed were radioimmunoassay (RIA), enzyme immunoassay (EIA), high performance liquid chromatography (HPLC), gas chromatography with electron capture detector (GC/ECD), and gas chromatography/mass spectrometry (GC/MS). A comparison of the results showed significant correlations between the results obtained by HPLC, GC/ECD, and GC/MS procedures. As anticipated, quantitation by any of these procedures resulted in lower values than those obtained by either of the immunoassays.