Surface treatments for capillary electrophoresis of proteins

The performance of Capillary Electrophoresis applied to the analysis of pro teins can be considerably improved by using a pre-treated capillary present ing a permanent hydrophilic layer immobilised on the capillary surface. The protein/surface interactions are then reduced or eliminated, resulting in an increased efficiency of separation. Some difficult analyses become possi ble, such as the analysis of basic proteins which are irreversibly adsorbed on a silica wall, The use of pre-treated tubes allows to improve the repro ducibility of the analyses, as the electroosmotic flow is better controlled in a broader range of pH. This review examines the various processes used to modify permanently the wall of a silica capillary. Two different approac hes are possible: i/ adsorption and immobilisation of a hydrophilic layer, ii/ covalent bonding of a stationary phase (ligand or macromolecule) having no affinity with the proteins analysed.