pH hysteresis effect with silica capillaries in capillary zone electrophoresis

Abstract

Electroosmotlc mobility was determined as a function of pH at constant Ionic strength by using a neutral marker. It was observed that the electroosmotlc mobility was dependent on the preconditioning of the fused silica column. The electroosmotlc 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.

Effects of injector geometry and sample matrix on injection and sample loading in integrated capillary electrophoresis devices

“…Changes in composition can affect electroosmotic mobility and thus change the migration velocity and consequently the peak areas. This effect can be compensated for by dividing peak area by migration time to obtain a quantity proportional to the number of molecules injected [29], as we have done in this study. Signal magnitudes varied from day to day or chip to chip; comparisons of intensity or peak area presented below were therefore made between matched data sets (i.e., same day, same chip).…”

Determination of Histamine by Capillary Zone Electrophoresis with Amperometric Detection

“…13 Different capillary pretreatments result in different charges on the capillary surface. Figure 3 shows the electropherograms of histamine when the capillary was treated differently.…”

Determination of dissociation constants of amino acids by capillary zone electrophoresis

“…At the higher pH, however, the silanol groups are fully charged and the zeta potential becomes higher. In CZE, the pH hysteresis effect with silica capillary has been described by Lambert and Middleton [25]. They stated that the equilibration of the surface charge on the fused silica surface appeared to be a relatively slow phenomenon and the electroosmotic mobility depended on the preconditioning of the fused-silica column.…”