Analysis of 11-nor-9-carboxy-Δ9-tetrahydrocannabinol in urine by LC-MS-MS after stir-bar sorptive extraction and liquid desorption

In this study, we established a detailed procedure for analysis of 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCA), the main metabolite of Δ9-tetrahydrocannabinol, in human urine by liquid chromatography-tandem mass spectrometry (LC-MS-MS) using SBSE with liquid desorption. For quantitative analysis, an external calibration method was used. A urine sample was fi rst hydrolyzed under strong alkaline conditions, followed by SBSE with a Twister stir bar at about pH 3. The analyte was desorbed from the bar with a small amount of ethyl acetate. After evaporation of the solvent, it was reconstituted in water-methanol mixture for LC-MS-MS analysis in the selected reaction monitoring mode. The calibration curve for THCA was linear in the range of 10–200 ng/ml urine. The lower limit of de...

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