LAUSR

The aim of this work was to develop and validate a liquid chromatography tandem mass spectrometry method for detecting of the main cannabinoids, of cannabinol (CBN) and tetrahydrocannabinol (THC) and the primary metabolite 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH) in hair samples. Extraction of the cannabinoids was carried out by a polymeric strong anion mixed mode solid phase extraction cartridge and then employing methanolic HCl followed by 2-fluoro-1-methyl pyridinium-p-toluenesulfonate (FMP-TS) as a derivatization procedure of carboxyl and phenolic groups respectively offering enhanced sensitivity for the detection of THC-COOH in hair matrices. Formation of a methyl ester increased its lipophilicity and removed the negative charge on the carboxyl group. Calibration curves were prepared over the range of 0.02-4 pg/mg of hair for THC and CBN and 0.2-12 pg/mg of hair for THC-COOH. The extraction recovery was between 81% to 105 % for all compounds. The limit of detection (LOD) and quantification (LOQ) were 2 and 20 pg/mg respectively for both CBN and THC and 0.1 and 0.2 pg/mg respectively for THC-COOH, which met the society of hair testing recommendation. Intra- and inter-assay precision were always lower than 4 and 11% respectively for these cannabinoids. Whereas, intra- and inter-assay bias were between 14 and -18 % and 15 and -12 % respectively. Twenty-seven hair specimens from cannabis users were investigated. The concentrations of CBN, THC and THC-COOH gave ranges of (0.022-2.562 ng/mg), (0.049-0.431 ng/mg) and (0.222-4.867 pg/mg) respectively. This new method of derivatization improves the LOD to ensure detection of the metabolite.