Manipulation of electroosmotic flow in capillary electrophoresis

This paper reports the use of surfactant and polymer-C18 coated capillaries that allow manipulation of electroosmotic flow (EOF). Although this approach to the control of EOF involves the preparation and use of multiple capillaries, all the coatings were prepared by a single procedure. It is shown that the ability to control EOF allows optimization of both separation time and resolution. In the case of proteins, low EOF maximizes resolution whereas high flow gives the shortest analysis time. It should be noted that proteins are a special case and this conclusion may not be true with other molecular species. Through selection of a specific coating, it is possible to complete a separation in the shortest time while maintaining sufficient resolution to give baseline resolution of proteins. The various coated capillaries were examined in capillary zone electrophoresis (CZE) and capillary isoelectric focusing (cIEF) separations of native protein standards and hemoglobin variants. Separation of glycosylated hemoglobin A1 variants was achieved by cIEF within 10 min, including the focusing time. Good run-to-run reproducibility was obtained by flushing the capillary with the coating solution between analyses.