CAPILLARY ZONE ELECTROPHORESIS OF PROTEINS WITH HYDROPHILIC FUSED-SILICA CAPILLARIES

Fused-silica capillaries having surface-bound hydroxylated polyether functions were developed for the separation of proteins by capillary zone electrophoresis. In one approach, the hydrophilic coatings consisted of two layers: a glyceropropylpolysiloxane sublayer covalently attached to the inner surface and a polyether top layer. In a second approach, the capillary wall was coated with polysiloxane polyether chains the monomeric units of which at both ends were covalently attached to the capillary inner surface with possible interconnection. These coatings yielded capillaries with different electroosmotic flow characteristics. The relatively long polyether chains of the various coatings were effective in shielding the unreacted surface silanols, thus minimizing solute-wall adsorption. As a consequence, high separation efficiencies were obtained in the pH range 4.0-7.5, which allowed the separation of widely differing proteins, the characterization of heterogeneous proteins and the fingerprinting of crude protein mixtures. The various coatings were stable and exhibited reproducible separations from run-to-run, day-to-day, and column-to-column. Furthermore, a procedure was developed for restoring collapsed capillaries after prolonged use.