Published: Journal of Analytical Toxicology, Volume 20, Number 7, November/December 1996, pp. 573-578.

A GC–MS Study of Three Major Acidic Metabolites of D1-Tetrahydrocannabinol
Maria Szirmai, Olof Beck, Nikolaj Stephansson, and Magnus M. Halldin

The major urinary metabolite of D1-tetrahydrocannabinol (D1-THC) (1), D1-THC-7-oic acid (2), has been extensively studied for several purposes, including testing in the workplace for drug abuse. Immunoassays in combination with more specific methods such as gas chromatography–mass spectrometry (GC–MS), are commonly used for verification of positive results in the screening. Two additional and recently synthesized acidic metabolites of 1, 4",5"-bisnor-D1-THC-7,3"-dioic acid (3) and 4"-hydroxy-D1-THC-7-oic acid (4), were studied to widen the scientific basis in the analysis. Five different derivatives were examined using GC–MS. In addition, a new deuterated internal standard for 2, [2H10]-2, was evaluated. According to our results, suitable derivatives of 2, 3, and 4, according to chromatographic properties, are the methyl ester/silyl ether (procedure a), the methyl ester/trifluoroacetate (procedure b), or the silyl ester/silyl ether (procedure c). The estimated recoveries of [2H5]-3 and [2H6]-4 using liquid–liquid extraction were 24% and 50%, respectively. The properties of [2H10]-2 as internal standard were equivalent to those of [2H9]-2 and, under the conditions used, did not appear to give rise to a significantly higher chromatographic resolution from that of 2. However, [2H10]-2 produces ions at different mass numbers, which makes it useful as a complement to the existing deuterated internal standards of 2.

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