Abstract:

Objective To establish an LC-MS/MS method based on single hair micro-segmental technique, and verify the detection of 42 psychoactive substances in 0.4 mm hair segments. Methods Each piece of single hair was cut into 0.4 mm segments and extracted by sonication and the segments were immersed in dithiothreitol-containing extraction medium. Mobile phase A was the aqueous solution containing 20 mmol/L ammonium acetate, 0.1% formic acid, and 5% acetonitrile. Mobile phase B was acetonitrile. An electrospray ionization source in positive ion mode was used for data acquisition in multiple reaction monitoring （MRM） mode. Results The 42 psychoactive substances in hair had a good linear relationship within their respective linear ranges （r>0.99）, the limits of detection were 0.2-10 pg/mm, the limits of quantification were 0.5-20 pg/mm, the intra-day and inter-day precisions were 1.5%-12.7%, the intra-day and inter-day accuracies were 86.5%-109.2%, the recovery rates were 68.1%-98.2%, and the matrix effects were 71.3%-111.7%. The method was applied to hair samples collected from one volunteer at 28 d after a single dose of zolpidem, with zolpidem detected in 5 hairs was 1.08-1.60 cm near the root tip, and the concentration range was 0.62-20.5 pg/mm. Conclusion The micro-segmental technique of single hair analysis can be applied to the investigation of drug-facilitated sexual assault cases.

Key words: forensic medicine, toxicological analysis, psychoactive substance, micro-segmentation, single hair, liquid chromatography-tandem mass spectrometry （LC-MS/MS）, zolpidem, drug-facilitated sexual assault