SOLUTE RETENTION IN ELECTROCHROMATOGRAPHY BY ELECTRICALLY INDUCED SORPTION

Column chromatography and electrophoresis are combined in electrochrom atography, where an electric potential is applied to a chromatography column in the axial direction. These studies utilized a dextran gel st ationary phase and an eluent of low ionic strength, which were chosen to minimize electric current and therefore column heating and undesira ble dispersion effects. The gel, with a small ion exchange capacity of several microequivalents per mL, turned out to be more conductive tha n the eluent and was able to concentrate macromolecules in the presenc e of combined electric and flow fields. The model presented describes solute retention due to electrically induced concentration polarizatio n of solute on the resin surfaces, as well as electrophoresis in the m obile and stationary phases. The polarization effect explains differen ces between retention of high-molecular-weight solutes with exclusion coefficients of less than 1 and that of a charged low-molecular-weight solute, which is hypothesized to pass through the gel matrix in the p resence of an electric field and does not experience concentration pol arization. It also shows the application of this effect for protein se paration in a liquid chromatography system with a superimposed electri c potential.