Published: Journal of Analytical Toxicology, ISSN 0146-4760, Volume 31, Number 8, October, pp.477-485

Simultaneous GC–EI-MS Determination of D9-Tetrahydrocannabinol, 11-Hydroxy-D9-Tetrahydrocannabinol, and 11-nor-9-Carboxy- D9-Tetrahydrocannabinol in Human Urine Following Tandem Enzyme-Alkaline Hydrolysis
Tsadik T. Abraham[1], Ross H. Lowe[1], Stephane O. Pirnay[1,2], William D. Darwin[1], and Marilyn A. Huestis[1],
[1]Chemistry and Drug Metabolism, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 5500 Nathan Shock Drive, Baltimore, Maryland, 21224 and
[2]Université Paris Descartes, Faculté de Pharmacie, Neuropsychopharmacologie des Addictions, CNRS, UMR7157 et Université Paris 7, INSERM, U705, Paris F-75010, France

A sensitive and specific method for extraction and quantification of Δ9-tetrahydrocannabinol (THC), 11-hydroxy-Δ9-tetrahydrocannabinol (11-OH-THC), and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH) in human urine was developed and fully validated. To ensure complete hydrolysis of conjugates and capture of total analyte content, urine samples were hydrolyzed by two methods in series. Initial hydrolysis was with Escherichia coli β-glucuronidase (Type IX–A) followed by a second hydrolysis utilizing 10N NaOH. Specimens were adjusted to pH 5–6.5, treated with acetonitrile to precipitate protein, and centrifuged, and the supernatants were subjected to solid-phase extraction. Extracted analytes were derivatized with BSTFA and quantified by gas chromatography–mass spectrometry with electron impact ionization. Standard curves were linear from 2.5 to 300 ng/mL. Extraction efficiencies were 57.0–59.3% for THC, 68.3–75.5% for 11-OH-THC, and 71.5–79.7% for THCCOOH. Intra- and interassay precision across the linear range of the assay ranged from 0.1 to 4.3% and 2.6 to 7.4%, respectively. Accuracy was within 15% of target concentrations. This method was applied to the analysis of urine specimens collected from individuals participating in controlled administration cannabis studies, and it may be a useful analytical procedure for determining recency of cannabis use in forensic toxicology applications.

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