FUNDAMENTAL AND PRACTICAL ASPECTS OF COUPLED CAPILLARIES FOR THE CONTROL OF ELECTROOSMOTIC FLOW IN CAPILLARY ZONE ELECTROPHORESIS OF PROTEINS

This article represents an extension to a new approach, which was introduced very recently by our laboratory, for the control of the magnitude of electroosmotic flow in capillary zone electrophoresis. In this new approach, short fused-silica capillaries having different potentials were coupled in series and the amount of the electroosmotic flow was conveniently varied by changing the lengths of the individual capillary segments. The different coupled capillary systems evaluated in this study comprised various combinations of untreated fused-silica capillaries and polyether-coated capillaries having various electroosmotic flow characteristics. A general equation relating the average electroosmotic flow velocity in the coupled capillaries to the intrinsic electroosmotic velocity of the connected segments and their corresponding lengths has been derived and verified experimentally. The rate of the electroosmotic flow in a given system of coupled capillaries could be tuned over a range bordered by the lowest and highest intrinsic flow-rates of the connected capillary segments. In addition, a system of coupled capillaries that permitted a stepwise change in the rate of the electroosmotic flow during analysis was introduced and evaluated. These elution schemes were useful in the rapid separation of oppositely charged proteins in a single electrophoretic run and in the rapid analytical determination of the various components of heterogeneous proteins.