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Abstract
A new method for detecting and quantifying 11-nor-9-carboxy-Δ8-tetrahydrocannabinol (Δ8-THC-COOH) in urine is proposed. The analyte is released as a glucuronide derivative into urine, so the glucuronide bond must be cleaved by alkaline hydrolysis prior to analysis. Subsequently, the sample is subjected to liquid-liquid extraction with n-hexane/ethyl acetate, followed by derivatization with a mixture of pentafluoropropionic anhydride (PFPA) and pentafluoropropanol (PFP-OH). Finally, the analyte is determined by capillary gas chromatography-mass spectrometry, using electron impact (EI) ionization. Quantitation is done by monitoring four ions in the single ion mode (SIM), using ethaverine as internal standard. The calibration graph is linear over the range 10–50 μg/mL and an average extraction yield of 90.50% is obtained. The proposed method is quite reproducible and exhibits a low limit of detection that affords quantitation of the analyte in urine samples from cannabis users.