Determination of 11-nor-Delta(9)-tetrahydrocannabinol-9-carboxylic acid inurine using high-performance liquid chromatography and electrospray ionization mass spectrometry

High-performance liquid chromatography with electrospray ionization mass sp ectrometry was used to determine 11-nor-Delta(9)-tetrahydrocannabinol-9-car boxylic acid (THC-COOH) in urine. After basic hydrolysis of conjugates, the compound was extracted using SPEC-PLUS-3ML-C-18 solid-phase extraction col umns. A deuterium labelled internal standard (d(3)-THCCOOH) was added prior to hydrolysis. Separation was performed on a reversed-phase Zorbax Eclipse XDB-C-8 analytical column (150x3.0 mm LD.) using a gradient program from 6 0 to 80% acetonitrile (4 mM formic acid) at a flow-rate of 0.5 ml/min. The compounds were detected by single ion monitoring of m/z 345 and m/z 348 for the protonated molecules [THC-COOH+H](+) and [d(3)-THC-COOH+H](+), respect ively. The precision and accuracy were tested on spiked urine samples in th e range 2.5-125 ng/ml. The mean recovery was 95% (n=58), coefficients of va riations were 2.2-4.3% and the limit of detection 2 ng/ml. Diagnostic quali fying ions of THC-COOH (m/z 327 and m/z 299) and d(3)-THC-COOH (m/z 330) we re generated using up-front collision-induced dissociation. The relative io n intensities in clinical samples (n=21) were within +/-20% deviation compa red with standards. Using this tolerance and the presence of the ions m/z 3 27 and m/z 299 at the correct retention times as the acceptance criteria fo r identification of THC-COOH positive samples, the limit of detection was 1 5 ng/ml. The LC-MS method complies with the current recommendations on drug s of abuse testing, in which mass spectrometric detection is emphasized. (C ) 1999 Elsevier Science B.V. All rights reserved.