CATIONIC AND ANIONIC POLYMERIC ADDITIVES FOR WALL DEACTIVATION AND SELECTIVITY CONTROL IN THE CAPILLARY ELECTROPHORETIC SEPARATION OF PROTEINS IN FOOD SAMPLES

Both cationic and anionic polymeric additives were used for fe capilla ry electrophoretic separation of proteins in food samples. The cationi c polyelectrolyte polydiallyldimethylammonium chloride was more effect ive in minimizing protein-wall interactions at pH 3 than at pH 7, pres umably due to greater repulsion between the adsorbed polymer and prote ins. Improved resolution was observed in the presence of the co-additi ve sodium octanesulphonate, presumably due to ion-pairing interactions with protein sample components. The anionic polymer dextran sulfate p roduced relatively high efficiencies, 120000-180000 theoretical plates , for protein separation, presumably because the polymer adsorbed to t he capillary wall, rendering the surface more hydrophilic. In addition to reduced protein-wall interactions, improved resolution was observe d, presumably due to analyte-polymer ion-exchange/ion-pairing interact ions. When poly(vinyl sulphonic acid) was used instead of dextran sulf ate, broader profiles were obtained and fewer components were resolved , presumably due to reduced wall deactivation that is related to the l ower hydrophilicity of poly(vinyl sulphonic acid). (C) 1998 Elsevier S cience B.V. All rights reserved.