Quantification of 11-nor-9-carboxy-δ9-tetrahydrocannabinol in human oral fluid by gas chromatography-tandem mass spectrometry.

A sensitive and specific method for the quantification of 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH) in oral fluid collected with the Quantisal and Oral-Eze devices was developed and fully validated. Extracted analytes were derivatized with hexafluoroisopropanol and trifluoroacetic anhydride and quantified by gas chromatography-tandem mass spectrometry with negative chemical ionization. Standard curves, using linear least-squares regression with 1/x weighting were linear from 10 to 1000 ng/L with coefficients of determination >0.998 for both collection devices. Bias was 89.2%-112.6%, total imprecision 4.0%-5.1% coefficient of variation, and extraction efficiency >79.8% across the linear range for Quantisal-collected specimens. Bias was 84.6%-109.3%, total imprecision 3.6%-7.3% coefficient of variation, and extraction efficiency >92.6% for specimens collected with the Oral-Eze device at all 3 quality control concentrations (10, 120, and 750 ng/L). This effective high-throughput method reduces analysis time by 9 minutes per sample compared with our current 2-dimensional gas chromatography-mass spectrometry method and extends the capability of quantifying this important oral fluid analyte to gas chromatography-tandem mass spectrometry. This method was applied to the analysis of oral fluid specimens collected from individuals participating in controlled cannabis studies and will be effective for distinguishing passive environmental contamination from active cannabis smoking.