MIGRATION BEHAVIOR AND SELECTIVITY OF SULFONAMIDES IN CAPILLARY ELECTROPHORESIS

The migration behavior and selectivity of thirteen sulfonamides in cap illary electrophoresis (CE), with emphasis on micellar electrokinetic chromatography (MEKC) were systematically investigated using a phospha te-borate buffer electrolyte, with sodium dodecyl sulfate (SDS) as an anionic surfactant in MEKC. The optimization strategies for the separa tion of sulfonamides in capillary zone electrophoresis (CZE) and in ME KC are described. The migration behavior and selectivity of sulfonamid es in CZE are mainly manipulated by the pH of the buffer. The migratio n order of sulfonamides depends on the ratios of charge to mass (q/M-2 /3) and is primarily determined by their pK(a) values. Thus precise op timization of buffer pH is crucial to further improve the separation o f some closely migrating sulfonamides. On the other hand, buffer pH an d micelle concentration greatly affect the migration and selectivity o f sulfonamides in MEKC. The migration order of sulfonamides is mainly determined by their pK(a) values and the magnitude of the binding cons tants of solutes-to-micelles. The influences of buffer pH and micelle concentration correlate with each other. The magnitude of the binding constants correlates with the differences between the electrophoretic mobility of sulfonamides measured at a pH below pK(a)-2 in CZE and tha t in MEKC. In this work, acid dissociation constants of these sulfonam ides and binding constants of sulfonamides to SDS micelles in a phosph ate-borate buffer are reported. (C) 1997 Elsevier Science B.V.