Simultaneous determination of selegiline-N-oxide, a new indicator for selegiline administration, and other metabolites in urine by high-performance liquid chromatography-electrospray ionization mass spectrometry

In order to discriminate selegiline (SG) use from methamphetamine (MA) use, the urinary metabolites of SG users have been investigated using high-perf ormance liquid chromatography (HPLC)-electrospray ionization mass spectrome try (HPLC-ESI-MS). Selegiline-N-oxide (SGO), a specific metabolite of SG, w as for the first time detected in the urine, in addition to other metabolit es MA, amphetamine (AP) and desmethylselegiline (DM-SG). A combination of a Sep-pak C,, cartridge for the solid-phase extraction, a semi-micro SCX col umn (1.5 mm I.D.X150 mm) for HPLC separation and ESI-MS for detection provi ded a simple and sensitive procedure for the simultaneous determination of these analytes. Acetonitrile-10 mM ammonium formate buffer adjusted to pH 3 .0 (70.30, v/v) at a flow-rate of 0.1 ml/min was found to be the most effec tive mobile phase. Linear calibration curves were obtained over the concent ration range from 0.5 to 100 ng/ml for all the analytes by monitoring each protonated molecular ion in the selected ion monitoring (SIM) mode. The det ection limits ranged from 0.1 to 0.5 ng/ml. Upon applying the scan mode, 10 -20 ng/ml were the detection limits. Quantitative investigation utilizing t his revealed that SGO was about three times more abundant (47 ng/ml, 79 ng/ ml) than DM-SG in two SG users' urine samples tested here. This newly-detec ted, specific metabolite SGO was found to be an effective indicator for SG administration. (C) 2001 Elsevier Science BN. All rights reserved.