Simultaneous analysis of Δ9-tetrahydrocannabinol and 11-nor-9-carboxy-tetrahydrocannabinol in hair without different sample preparation and derivatization by gas chromatography–tandem mass spectrometry

The present study describes a gas chromatography/tandem mass spectrometry-negative ion chemical ionization assay (GC/MS/MS-NCI) for simultaneous analysis of Δ9-tetrahydrocannabinol (THC) and 11-nor-9-carboxy-tetrahydrocannabinol (THCCOOH) in hair. Each hair sample, of approximately 20 mg, was weighed and the sample was dissolved in 1 ml of 1 M sodium hydroxide (30 min at 85 °C) in the presence of THC-d3 and THCCOOH-d3. For the analysis of THC, hair samples were extracted with n-hexane:ethyl acetate (9:1) two times; acetic acid and sodium acetate buffer were added for the analysis of THCCOOH, and hair samples were re-extracted with n-hexane:ethyl acetate (9:1) two times. The extracts were then derivatized with pentafluoropropionic anhydride (PFPA) and pentafluoropropanol (PFPOH). This method allowed the analysis of THC and THCCOOH using the GC/MS/MS-NCI assay. This method was also fully validated and applied to hair specimens (n = 54) collected from known cannabis users whose urine test results were positive. The concentrations of THC and THCCOOH in hair ranged from 7.52 to 60.41 ng/mg and from 0.10 to 11.68 pg/mg, respectively.In this paper, we simultaneously measured THC and THCCOOH in human hair using GC/MS/MS-NCI without requiring different sample preparation and derivatization procedures. The analytical sensitivity for THCCOOH in hair was good, while that for THC in hair needs to be improved in further study.