Detection and confirmation of urinary cannabinoids

Both a thin layer chromatographic procedure (TOXI-LAB) and two homogeneous immunoassays with differing sensitivity limits (EMIT-st, and EMIT d.a.u.) were used to test 525 urine specimens for metabolites of tetrahydrocannabinol. Negative results were obtained by all techniques for 283 specimens. The EMIT-st was positive for 184 specimens, the EMIT-d.a.u. for 47 additional specimens. The TOXI-LAB results were positive for all these 231 specimens. An additional 11 specimens were positive by EMIT-d.a.u. and negative by TOXI-LAB. Gas chromatography/mass spectrometry analyses of five of these 11 indicated that their average 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid concentration was 7.4 +/- 2.2 ng/mL, well below the lower detection limit of the TOXI-LAB procedure. Using both EMIT-d.a.u. and TOXI-LAB assures a reliable urinary cannabinoid analysis above a concentration of 25 ng/mL.