Theoretical Description of the Influence of External Radial Fields on the Electroosmotic Flow in Capillary Electrophoresis

Abstract

The effect of applying a radial voltage on the electroosmotic flow in capillary electrophoresis has been studied from a theoretical point of view. Based on Stern's model for the electric double layer on the surface of a fused silica capillary and on the Gouy-Chapman theory for the diffuse layer, equations describing the relation between the electroosmotic mobility and the radial electric field were derived. The thickness of the stagnant solution layer on the surface of the capillary, an important parameter in the calculations, was estimated from the electroosmotic mobility found in high-pH solutions. The theory developed predicts the experimental findings that the effect of the radial field levels off at high applied voltages and that it is smaller when the electroosmotic mobility without radial field is already high. The theoretical results were compared with experimental data taken from the literature. A good quantitative agreement was found.