A sensitive thin-layer chromatographic procedure for the detection of urinary 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid.

A sensitive high-performance thin-layer chromatographic (HPTLC) procedure for the detection of 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH), the major urinary metabolite of delta 9-tetrahydrocannabinol (THC), is described. After alkaline hydrolysis, the THC-COOH is extracted from acidified urine into hexane. The hexane is evaporated and the residue spotted onto an HPTLC plate. Chromatography time is 11 min with heptane/butanol/acetic acid (90:9:1) as mobile phase. The cannabinoids are visualized by sequentially dipping the thin-layer plate in diethylamine then in 0.1% Fast Blue BB. The limit of detection for THC-COOH is 5 ng/mL when 2 mL of urine is used. Extraction efficiencies averaged 71% over the 10-400 ng/mL range. No drugs, drug metabolites, or endogenous urinary substances interfere with the procedure.