Simultaneous analysis of some amphetamine derivatives in urine by nonaqueous capillary electrophoresis coupled to electrospray ionization mass spectrometry

A nonaqueous capillary electrophoresis method, coupled to UV and electrospray mass spectrometry (ESI-MS), is described for the simultaneous analysis of Ecstasy and other related derivatives. Several electrophoretic and ESI-MS parameters were systematically investigated, such as electrolyte nature and concentration, organic solvent and sheath liquid compositions, nebulization gas pressure and drying gas flow-rate. The best results were achieved with an acetonitrile–methanol (80:20, v/v) mixture containing 25 mM ammonium formate and 1 M formic acid, an applied voltage of 30 kV and a separation temperature of 15°C. Under optimized CE–ESI-MS conditions, separation of the investigated drugs was performed in less than 6 min, with a high efficiency. Method precision based on migration time and peak area was determined and the limits of detection, which depend on the tested compound, were established between 20 and 70 ng ml−1 in the selected ion monitoring mode. Finally, the described method was successfully applied to the analysis of amphetamines in urine after a liquid–liquid extraction.