Separation of basic drugs with non-aqueous capillary electrophoresis

Capillary zone electrophoresis (CZE) was investigated in non-aqueous media. Efficient, rapid and versatile electrophoretic conditions were obtained with 20 mM ammonium acetate in acetonitrile-methanol-acetic acid (49:50:1). Using this non-aqueous medium, the baseline separation of nine morphine analogues, eleven antihistamines, eleven antipsychotics and ten stimulants could each be achieved in 6 min. The migration order observed was very different from one expected for an aqueous medium. The migration time repeatability for individual components was between 0.8 and 3.7\% R.S.D. The migration time-normalized peak area had a poor precision; however, with one of the components as an internal reference, the quantitative repeatability could be improved to between 2.2 and 9.1\% R.S.D. The precision data appeared to be instrument dependent, as excellent results could be obtained from an instrument with better evaporation and temperature control. Alternatively, much improved speed, efficiency and precision were also achieved with tetra-n-butylammonium tetrafluoroborate as the electrolyte, albeit with reduced selectivity. The effects of the electrolyte, non-aqueous medium and applied voltage on the separation are discussed