Gas Chromatography-Mass Spectrometry Analysis of 11-Nor-9-carboxy-Δ9-Tetrahydrocannabinol in Urine
DONG-LIANG LIN1,2*, TSUNG-LI KUO2 AND RAY H. LIU3
1. Scientific and Technical Research Center, Ministry of Justice Investigation Bureau, P.O. Box 3562, Taipei, Taiwan, R.O.C.
2. Department of Legal Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan, R.O.C.
3. Graduate Program in Forensic Science, University of Alabama at Birmingham, AL, 35294 U.S.A.
ABSTRACT
Effective specimen pretreatment and GC-MS protocols were developed for the analysis of 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH) in urine. d3- and d9-11-nor-9-carboxy-Δ9-tetrahydrocannabinol (d3- and d9-THC-COOH) were evaluated as internal standards and conclusions were reached that THC-COOH can be effectively analyzed, qualitatively and quantitatively, as trimethylsilyl derivative using selective ion monitoring of the following ions: m/z 371, 473 and 488 (for THC-COOH) and m/z 380, 479 and 497 (for d9-THC-COOH). The extraction procedure achieved 90% recovery of the analyte in fortified drug-free urine containing 10-200 ng/ml THC-COOH. Using 2-ml sample size, the overall protocol resulted in the following analytical parameters in the 10-200 ng/ml concentration range studied: interday and intraday precision ranges, 0.35-5.31% and 0.44-5.19%, respectively; linearity, r
2 > 0.999.
Key words: GC-MS, internal standard, 11-nor-9-carboxy-Δ9-tetrahydrocannabinol, urine, drug of abuse