Simultaneous determination of selegiline, desmethylselegiline, R/S-methamphetamine, and R/S-amphetamine in oral fluid by LC/MS/MS

Abstract

It is crucial for forensic analysis to differentiate clinical use from illegal abuse. Selegiline (SG) is mainly metabolized to desmethylselegiline (DM-SG), R-(−)-methamphetamine (R-MA) and R-(−)amphetamine (R-AM); while abused methamphetamine and amphetamine mainly contain the S-(+)-form. The aim of this study was to simultaneously determine SG, DM-SG, R/S-MA, and R/S-AM in human oral fluid (OF) and to differentiate clinical use from illegal use. We also aim to apply the present method to the OF samples from authentic cases in forensic toxicology. Liquid–liquid extraction and liquid chromatography-tandem mass spectrometry operating in positive ion multiple-reaction monitoring mode were utilized. The chromatographic system consisted of a ChirobioticTM V2 column (2.1 mm × 250 mm, 5 μm) and a mobile phase of methanol containing 0.1% (v/v) glacial acetic acid and 0.02% (v/v) ammonium hydroxide. The calibration curves were linear from 1 to 100 ng/mL, and r > 0.995 for all analytes with imprecisions ≤ 15% and accuracy between 85 and 115%. Extraction recoveries ranged from 46.3 to 104.7% with coefficient of variation (CV) ≤ 10.3% and matrix effects (MEs) ranged from 47.4 to 114.8% with CV ≤ 12.9%. The lower limit of quantification was 0.2 ng/mL for SG and DM-SG and 1.0 ng/mL for S-MA, R-MA, S-AM and R-AM. The present method is simple, rapid (accomplished in 12 min), sensitive, and validated by authentic samples.