Detection of 11-nor-9-carboxy-tetrahydrocannabinol in the hair of drug abusers by LC-MS/MS analysis

摘要

Cannabis is the second most commonly abused illicit drug after methamphetamine in South Korea. To prove cannabis consumption, 11-nor-9-carboxy-tetrahydrocannabinol (THC-COOH), the metabolite of tetrahydrocannabinol (THC), was screened for in a hair analysis. In this study, we developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis method, which was used to analyze authentic hair samples in 2017. Possible contaminants on the surface of hair samples were eliminated by washing twice each with 2 mL of methanol and distilled water. After adding an internal standard (THCCOOH-d(3)), the hair samples (about 20 mg each) were digested with 1 M NaOH, extracted twice with mixed organic solvents (n-hexane:ethyl acetate), and analyzed by an LC-MS/MS system. Identification and quantification of THC-COOH and THC-COOH-d(3) were performed using a multiple reaction monitoring (MRM) mode at m/z 245 and 191 and m/z 248, respectively (quantifier ions are underlined). The following validation parameters were evaluated: selectivity, linearity, limit of detection (LOD), limit of quantification (LOQ), precision, accuracy, matrix effect, and recovery. The LOD and LOQ of the method was 0.1 pg/mg. Good linearity was achieved for THC-COOH in the range from 0.1 to 20 pg/mg. The method showed an acceptable precision and accuracy, both of which were less than 15% at the three concentrations of THC-COOH (0.2, 1, and 10 pg/mg). THC-COOH showed ion suppression at these three concentrations. The concentrations of THC-COOH in the authentic hair samples ranged from 0.10 to 27.30 pg/mg (total 586 cases), and its concentrations were classified as low, medium, or high ranges, i.e., 0.10-0.39 pg/mg, 0.39-1.99 pg/mg, or 1.99-27.30 pg/mg, respectively, according to statistical evaluation. This method showed the possibility of replacing the existing gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis. However, further development of our LC-MS/MS method is necessary in order to meet the recommended 0.05 pg/mg cut-off. (C) 2018 Elsevier B.V. All rights reserved.