GAS-CHROMATOGRAPHIC MASS-SPECTROMETRIC QUANTITATION OF URINARY 11-NOR-DELTA-9-TETRAHYDROCANNABINOL-9-CARBOXYLIC ACID AFTER DERIVATIZATION BY DIRECT EXTRACTIVE ALKYLATION

A gas chromatographic-mass spectrometric procedure for the quantitation of urinary 11-nor-DELTA9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) has been developed in which the THC-COOH was derivatized to its corresponding methyl ester-methyl ether derivative by direct extractive alkylation using tetrahexylammonium (THA+) counter-ion and iodomethane dissolved in toluene. The procedure utilised a sample volume of 2 ml and gave a detection limit of 0.25 ng/ml. The inter-run and intra-run coefficients of variation were 7.0% and 4.8%, respectively. The inter-day standard curves were linear in the concentration range 0-300 ng/ml with a mean r = 0.9997 (n = 4).