Rapid method for the GC/MS confirmation of 11-nor-9-carboxy-delta 9-tetrahydrocannabinol in urine

A rigorously tested simple extraction procedure for the GC/MS determination of 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (THC-acid) from urine is described. This assay provides sensitivity, specificity and reliability and is particularly well suited for the routine determination of large numbers of samples. The THC-acid is detected as its trimethylsilyl derivative using electron impact ionization GC/MS with an on column detection limit below 1 ng/mL. The assay gives excellent reproducibility and linearity using the trideuterated analog of THC-acid as the internal standard. The procedure was evaluated with over 1300 samples and provided inter- and intra-day precision of 10% and 6% standard deviation, respectively.