Confirmation of cannabis use. II. Determination of tetrahydrocannabinol metabolites in urine and plasma by HPLC with ECD.

Simultaneous determination of delta 9-tetrahydrocannabinol (THC) and its major metabolites--11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) and 11-hydroxy-delta 9-tetrahydrocannabinol (11-OH THC)--in urine and plasma by HPLC with electrochemical detection (LC/EC) was studied. After biological fluids were hydrolyzed, samples were extracted with an automatic extractor and analyzed by LC/EC. HPLC was carried out with a reversed-phase silica C8 column and a mobile phase of acetonitrile/methanol/0.02N H2SO4 (35:15:50) at 1.8 mL/min. Coefficients of variation at 10-500 ng/mL of THC metabolites were 2.19-5.91%. The detection limit was under 0.5 ng/mL (S/N greater than 3). Time course of excretion of THC and THC-COOH in rabbit urine was studied. THC-COOH could be detected until 216 h after administration. By this method, urine samples of suspects arrested in Japan were tested.