PH HYSTERESIS EFFECT WITH SILICA CAPILLARIES IN CAPILLARY ZONE ELECTROPHORESIS

Eiectroosmotic mobility was determined as a function of pH at constant ionic strength by using a neutral marker. It was observed that the eiectroosmotic mobility was dependent on the preconditioning of the fused silica column. The electroosmotic mobility values that were obtained from a column previously exposed to acidic conditions for varying periods of time were consistently lower than the values from columns previously exposed to alkaline conditions, particularly in the pH 4–6 region. The equilibration of the surface charge on the fused silica surface appears to be a relatively slow phenomenon. Since the peak area In capillary zone electrophoresis varies inversely with the solute mobility, attention should be paid to capillary preconditioning, particularly in the pH 4–6 range. © 1990, American Chemical Society. All rights reserved.