Effect of a soluble ionic polymer on the separation of anions by capillary electrophoresis

A silica capillary for CE analysis of anions can be conditioned with NaOH, rinsed with water, coated with a cationic polymer, and equilibrated with the background electrolyte in only 2 min for each of the four steps. The coated surface has a positive charge that gives a substantial anodic electroosmotic flow (EOF) over the range of pH 2.5-12.0. The migration times of sample anions and a neutral marker (used for EOF calculations) are generally reproducible to an RSD of 1% or better, both for successive runs on a single capillary and from capillary to capillary. It was shown that the type of buffer used affects the EOF of a coated capillary. A concentration of 100 mM or higher sodium chloride minimizes differences in EOF with different buffers and also gives sharper peaks for sample anions.