Abstract: Capillary zone electrophoresis is enhanced by the application of an electric field across the interior of the capillary tube. This external electric field is applied through a conductive member at the exterior of the capillary tube. The external field vectorially couples with the internal field, controlling the polarity and the magnitude of the surface (zeta) potential on the interior surface of the capillary. The control of the surface (zeta) potential reduces adsorption of macromolecular onto the interior surface of the capillary tube, by inducing electrostatic repulsions between the macromolecules, and the capillary surface. Additionally, the control of the surface (zeta) potential can retard, and even reverse, electroosmotic flow, depending upon the magnitude of those fields.