Marijuana metabolites in urine of man : X. Identification of marijuana use by detection of Δ 9-tetrahydrocannabinol-11-OIC acid using thin-layer chromatography

Abstract

Marijuana use can be determined by detecting Δ 9-tetrahydrocannbinol-11-oic acid (THC-11-oic acid) in urine. For this, we describe a procedure for its chemical detection by using sequential thin-layer chromatography on a single plate for rapid isolation and identification. A volume of urine containing 50 mg of creatinine is concentrated by evaporation to 10 ml, the concentrate is enzymically hydrolyzed for 30 minutes and extracted with ether, and the extract is purified by treatment with NaHCO 3, then chromatographed in an alkaline and an acidic solvent sequence. The plate is sprayed with Fast Blue Salt B, and THC-11-oic is identified by its characteristic mobility and its characteristic colour reaction. The sensitivity is 0.5 μg. THC-11-oic acid has been detected in urines collected after the smoking of one standard cigarette containing 16–18 mg of Δ 9-tetrahydrocannabinol and in 34 of the first 100 tests of spontaneously collected urines of patients in a hospital drug-abuse treatment program. Multiple samples are easily carried through this extraction procedure. Evaporative concentration takes about 20 min per sample, and the analysis of eight concentrated samples takes about 5.5 h.