Confirmation of Syva Enzyme Multiple Immunoassay Technique (EMIT®) d.a.u. and Roche Abuscreen® Radioimmunoassay (RIA) (¹²⁵I) Urine Cannabinoid Immunoassays by Gas Chromatographic/Mass Spectrometric (GC/MS) and Bonded-Phase Adsorption/Thin-Layer Chromatographic (BPA-TLC) Methods

Thirty human urines screened positive by the Syva enzyme multiple immunoassay technique (EMIT®) d.a.u. urine cannabinoid assay were also positive for the major marijuana urinary metabolite 11-nor-Δ⁹-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) when assayed by gas chromatographic/mass spectrometric (GC/MS) and a noninstrumental qualitative bonded-phase adsorption/thin-layer chromatographic (BPA-TLC) technique. The noninstrumental BPA-TLC procedure was the simpler of the two techniques to perform and interpret. Assay of these same samples by the Roche Abuscreen® radioimmunoassay (RIA) for cannabinoids (¹²⁵I) revealed that reliance on the 100-ng/mL equivalent positive calibrator yielded a high incidence of false negative results (10 out of 30). The performance of these same 4 assays on 30 true negatives also was evaluated. All samples were negative for cannabinoids by EMIT and RIA, and for THC-COOH by BPA-TLC. GC/MS assay, however, detected spurious low levels of approximately S-ng/mL THC-COOH in two instances. Because of this, a reliability level of 10 ng/mL was set for the routine quantitative confirmation of THC-COOH by the GC/MS method.