A Method for the Determination of 11-Nor-Delta-9-Tetrahydrocannabinol-9-Carboxylic Acid in Urine Using High Performance Liquid Chromatography with Electrochemical Detection

11-Nor-delta-9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) was isolated using solid phase extraction and identified with high performance liquid chromatography (HPLC) with electrochemical detection (EC). HPLC/EC was compared to an established HPLC procedure using ultraviolet (UV) detection. Statistical analysis revealed good precision, linearity, and correlation between the HPLC/EC and HPLC/UV methods. Within-run and between-run precision for the HPLC/EC vs. HPLC/UV analyses yielded coefficients of variation of 4.1 vs. 6.7% and 8.3 vs. 10.9%, respectively. Standard curves over a range of 20 to 160 ng/mL of THC-COOH in fortified urine on four separate analytical runs yielded correlation coefficients of greater than 0.99 for each method. Quantitative results from 15 positive urine specimens also compared favorably between the two methods (r = 0.9923). Using an immunoassay screening technique with confirmation by HPLC/UV and high efficiency thin layer chromatography (HETLC), further evaluation of the HPLC/EC method was achieved by examining 50 cannabinoid positive and 50 cannabinoid negative clinical urine specimens and 500 sequentially collected postmortem urine specimens.