Poly(diallyldimethylammonium chloride) as a cationic coating for capillary electrophoresis

A novel cationic polymer coating that exhibits a fast anodal electroosmotic flow (EOF) has been developed for capillary electrophoresis. In the first approach, poly(diallyldimethylammonium chloride) is chemically bonded onto the interior capillary wall; in a second approach, the polymer is physically adsorbed onto the inner wall of the capillary. Capillaries modified by both approaches exhibit an anodal EOF in the pH range of 2.2-8.8, with a relatively pH-independent EOF (approximately -5.5 × 10-4cm2/V s) over the pH range of 2.2-5.5. The application of the novel EOF-reversed phase is demonstrated by the improved separation of basic proteins and beta-adrenergic blocking drugs. Separation efficiencies ranging from 50,000 to 200,000 plates per meter are observed for proteins. The relative standard deviation (RSD) of migration times for multiple injections of test proteins is less than 0.65%. The reproducibility of capillary synthesis is 2.3% RSD for capillaries synthesized on three different days. The lifetimes of both the bonded and physically coated capillaries exceed 40 h of continuous use at 240 V/cm at pH 4.