Pretreatment of urine samples for the analysis of 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid using solid-phase extraction.

An extraction and concentration procedure using a unique solid-phase extraction tube was developed for the analysis of 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid in urine. Absolute and relative recoveries of the drug metabolite were found to be greater than 85% and 92%, respectively. The extraction procedure allows quantitation of the drug metabolite by GC/MS, HPLC with UV detection, or GC with flame ionization detection. The extraction procedure was verified with urine samples obtained from marijuana users as well as spiked urine samples.