CAPILLARY ZONE ELECTROPHORESIS WITH EXTERNAL RADIAL ELECTRIC-FIELD CONTROL OF ELECTROOSMOTIC FLOW AND ITS APPLICATION TO THE SEPARATION OF SYNTHETIC OLIGOPEPTIDES

A new way of applying external radial electric field for the control o f electroosmotic flow in capillary zone electrophoresis (CZE) has been developed. It is based on a new type of low-conductivity coating of t he outer capillary surface by a polyaniline dispersion in hydroxypropy lcellulose and on the application of a set of three high-voltage power supplies to form a constant radial electric field across the capillar y wall as far as possible along the capillary length. Two power suppli es are connected to the ends of the outer low-conductivity coating and the third one is applied to the ends of the inner capillary compartme nt filled with background electrolyte, The difference of electric pote ntials at the inner and outer capillary surface determines the voltage of radial electric field across the capillary wall and affects the el ectrokinetic potential at the solid-liquid interface inside the capill ary. The effect of magnitude and polarity of external radial electric field on the how-rate of electroosmotic flow, on the migration times o f charged analytes (speed of analysis) and on the separation efficienc y and resolution of CZE separations of synthetic oligopeptides, diglyc ine, triglycine, dalargin and dalargin-ethylamide has been evaluated. Application of external radial electric field has proved to be an effi cient tool for regulation of electroosmotic flow in CZE and for optimi zation of migration times and resolution of oligopeptides in their CZE separations and analyses.