Determination of AB-CHMINACA and its metabolites in human hair and their deposition in hair of abusers

Despite global efforts to control the abuse of synthetic cannabinoids, the high-level of turnover from the market impedes regulation, endangering public health. N-[(1S)-1-(aminocarbonyl)-2-methylpropyl]-1-(cyclohexylmethyl)-1H-indazole-3-carboxamide (AB-CHMINACA) is the most popular synthetic cannabinoid in South Korea since its introduction in 2014. Nonetheless, few studies have been carried out on AB-CHMINACA and its metabolites, and its deposition in human hair. The purpose of this study was to develop and validate an analytical method for detection of AB-CHMINACA and its six metabolites in hair using a liquid chromatography tandem mass spectrometry (LC-MS/MS) system, for forensic applications. The methanol extracts of hair samples were evaporated, filtered, and analyzed by LC-MS/MS with electrospray ionization in positive ion mode. The limits of detection and quantification ranged from 0.5 to 10pg/mg and 2 to 50pg/mg, respectively. Good linearity was achieved within the range of 5-1000pg/mg or 10-1000pg/mg depending on the analyte. Intra- and inter-assay precision and accuracy values were below 15%. No significant variation was observed using different sources of hair matrices. These validation results proved the selectivity, accuracy and reproducibility of the method. The established method was applied to 37 authentic samples from suspected synthetic cannabinoid users. AB-CHMINACA and its two metabolites, AB-CHMINACA M2 and AB-CHMINACA M4, were detected. The concentration of the parent drug was much higher than those of its metabolites, and the amount of AB-CHMINACA M2 was greater than that of AB-CHMINACA M4 in all samples. No other metabolites were detected in the samples.