Quantitative studies on the adsorption of proteins to the bare silica wallin capillary electrophoresis III: Effects of adsorbed surfactants on quenching the interaction

The efficacy of two classes of surfactants, non-ionic and zwitterionic, in quenching the interaction of proteins with the naked silica wall in capilla ry electrophoresis, is evaluated. The class of non-ionic detergents is foun d to be rather inefficient in preventing protein binding to the fused-silic a surface, since large amounts (up to 10%) are required for reducing such i nteractions by 90%. Conversely, zwittergents appear to be much more efficie nt, since, in the case of sulphobetain SB-16, 90% binding inhibition is ach ieved at a concentration of surfactant of only 0.3%. In this last case, it is found that the binding inhibition closely follows the values of critical micellar concentrations (CMCs) of the various surfactants, those having th e lowest CMC value exhibiting the highest inhibition power. The CMC values also follow a hydrophobicity scale, suggesting that the most hydrophobic zw ittergents are the ones that shield more efficiently the silica surface. (C ) 2000 Elsevier Science BN. All rights reserved.