Migration behavior and separation of sulfonamides in capillary zone electrophoresis .2. Positively charged species at low pH

The migration behavior and separation of sixteen sulfonamides as positively charged species at low pH were systematically investigated by capillary zone electrophoresis using citrate buffer as a background electrolyte. Optimized separation parameters were determined. The results indicate that buffer pH and buffer concentration are two important separation parameters. However, buffer pH has a larger effect on the selectivity and resolution of sulfonamides than buffer concentration. In particular, the resolution of sulfamethizole and sulfamonomethoxine is improved with increasing buffer concentration, whereas that of sulfamerazine and sulfathiazole improves with increasing buffer pH, and that of sulfameter, sulfadimethoxine and sulfaquinoxaline improves with increasing buffer concentration and buffer pH. Complete separation of sixteen sulfonamides was achieved using citrate buffer (500 mM) at pH 2.1 and an applied voltage of 30 kV. Moreover, the migration order of sulfonamides is primarily determined by their pK(a1) values.