Rapid capillary coating by epoxy-poly-(dimethylacrylamide): Performance in capillary zone electrophoresis of protein and polystyrene carboxylate

A fast and simple method for the internal coating of capillaries in capillary zone electrophoresis (CZE) is that with epoxy‐poly(dimethylacrylamide) (EPDMA). Duration of coating by that method is 30 min, compared with that of 24 h when using uncross‐linked polyacrylamide (PA) under otherwise identical conditions. Under the conditions used for the CZE of proteins (pH 9.0, 2% polyethylene glycol), the capillary coating with EPDMA is stable for at least 50 consecutive runs as judged by the constancy of low electroosmotic flow, equalling the stability of coating achieved by PA. Protein mobilities and protein peak asymmetry (suggestive of reversible interaction with the capillary wall) are also found to be the same in EPDMA and PA coated capillaries. Differences between EPDMA and PA coating also exist: The former is unstable upon lowering the ionic strength of the buffer to 0.003, upon the addition of sodium dodecyl sulfate (SDS) to the buffer and in application to the hydrophobic analyte, polystyrene carboxylate.