Determination of XLR-11 and its metabolites in hair by liquid chromatography–tandem mass spectrometry

Abstract

Analysis of drugs in hair is often used as a routine method to obtain detailed information about drug ingestion. However, few studies have been conducted on disposition of synthetic cannabinoids including cyclopropylindoles (UR-144 and XLR-11) and their metabolites in hair. XLR-11 has been widely abused in South Korea recently. Identification of metabolites in hair can be an important proof of synthetic cannabinoids use because it can exclude the possibility of passive smoke exposure. In this study, we described a quantitative analytical method of XLR-11 and its metabolites (UR-144, UR-144 N-5-hydroxypentyl metabolite, UR-144 N-4-hydroxypentyl metabolite, UR-144 N-pentanoic acid metabolite and XLR-11 N-4-hydroxypentyl metabolite) in hair by liquid chromatography with ESI-MS/MS. The target analytes were extracted with methanol from washed and cut hair samples and the extracts were evaporated, filtered and analyzed by LC–MS/MS with electrospray ion source in positive-ionization mode. JWH-018-d9 and JWH-018 N-5-hydroxypentyl metabolite-d5 were used as internal standards. Chromatographic separation was completed within 15min. No interferences were detected in 10 blank hair samples. In intra- and inter-assay precision and accuracy study, CV (%) and bias (%) were below 12. The limit of detection (LOD) was 0.1∼2pg/mg and the limit of quantification (LOQ) was 0.2–2pg/mg, respectively. The validation results proved that the method was selective, accurate and precise with acceptable linearity within calibration range. No significant variation was observed by different sources of matrices. This method was applied to hair samples from 14 individual suspects of XLR-11 use. In this result, XLR-11, UR-144, UR-144 N-5-hydroxypentyl metabolite and UR-144 N-pentanoic acid metabolite, XLR-11 N-4-hydroxypentyl metabolite were detected. The concentration of XLR-11 as a parent drug was much higher than other metabolites. UR-144 N-5-hydroxy metabolite and UR-144 N-pentanoic acid were detected mainly in the authentic hair samples from suspected of XLR-11 use. UR-144 N-4- hydroxypentyl metabolite was not detected in all cases.