EFFECTS OF CARRIER ELECTROLYTE-COMPOSITION ON SEPARATION SELECTIVITY IN CAPILLARY ZONE ELECTROPHORESIS OF LOW-MOLECULAR-MASS ANIONS

A systematic investigation was carried out on the influence of carrier electrolyte composition on separation selectivity in capillary zone electrophoresis of inorganic anions. Chromate, chloride, sulphate or nitrate was used as the carrier electrolyte, each containing a quaternary ammonium salt to reverse the electro-osmotic flow. The concentration and nature of the carrier electrolyte salt affected the separation order only to a minor degree. Much more pronounced effects could be achieved by adding organic solvents to the carrier electrolyte or by using different quaternary ammonium salts. Chemical modification of the inner wall of the fused-silica capillary did not affect the migration order significantly. There is no indication of retention by effects similar to ion-interaction chromatography as long as capillaries with an inner diameter of 75 mum are used. Nevertheless, such effects might play an important role for capillaries with diameters of 10 mum or less.