External electric field control of electroosmotic flow in non-coated and coated fused-silica capillaries and its application for capillary electrophoretic separations of peptides.

The influence of an external electric field on the electroosmotic flow in the noncoated (bare) fused-silica capillaries and in the fused-silica capillaries with covalent coating of the inner surface by the polymer of a new acrylamido derivative, N-(acryloylaminoethoxy)ethyl-beta-D-glucopyranose, has been tested in the capillary electrophoretic separations of peptide analytes. The effect of magnitude and polarity of the external electric field on the flow-rate of the electroosmotic flow, the migration times of charged analytes and the separation efficiency and resolution of separations of synthetic oligopeptides, diglycine, triglycine, glycyl-proline and prolyl-glycine, by capillary zone electrophoresis has been evaluated. The effect of the external electric field on the velocity of the electroosmotic flow was much higher in the bare fused-silica capillaries than in the coated capillaries. Better separation of the analyzed peptides was achieved in the coated fused-silica capillaries. An external electric field proved to be an effective tool for control of the electroosmotic flow and for optimization of the speed and resolution of capillary electrophoretic separations of synthetic peptides.