MIGRATION BEHAVIOR AND SEPARATION OF SULFONAMIDES IN CAPILLARY ZONE ELECTROPHORESIS .3. CITRATE BUFFER AS A BACKGROUND ELECTROLYTE

摘要

To separate sulfonamides using capillary zone electrophoresis, citrate buffer is superior to phosphate buffer as a background electrolyte. Separation parameters affecting the selectivity and resolution of sulfonamides were optimized. Complete separation of thirteen sulfonamides was rapidly and efficiently achieved within 2.1 min with citrate buffer at pH 6.9. The resolution of peaks between sulfamethoxypyridazine and sulfathiazole, is enhanced either on heating the capillary to 35 degrees C or on adding methanol to the buffer electrolyte in an appropriate proportion. In combination with mobility data obtained at low pH, two pK(a) values of each individual sulfonamide are satisfactorily determined. Electrophoretic mobilities of sulfonamides measured at optimum pH of the buffer correlate well with those calculated from Offord's equation. Thus the order of migration of these sulfonamides, reflected in the magnitudes of their electrophoretic mobilities, depends on their ratios of charge to mass, and is primarily determined by their pK(a) values.