Capillary electrophoresis of anions in an untreated polypropylene hollow fiber

Capillary electrophoresis has been performed primarily in small-bore fused-silica capillaries. The walls of these capillaries are acidic, generating a large electroosmotic flow (EOF) at elevated pH. In order to reverse the high EOF in these capillaries to allow for early detection of the fast, inorganic anions, electroosmotic Row modifiers (OFMs) are added to the electrolyte or the walls of the capillary are covalently altered. Surface-modified, hollow polypropylene fibers have been employed recently for the separation of large biomolecules where sample adsorption to the walls of silica capillaries is a problem. The nonpolar inner surface of the polypropylene capillaries is an ideal site for graft copolymerization of polymeric coatings to aid in these separations. We have successfully used these polypropylene capillaries without wall modification, or addition of an OFM, to separate small, inorganic anions. Detection limits and resolution are comparable to those achieved using fused-silica capillaries and separations at elevated pH values are possible with this system.