A new method for performing continuous electrophoretic separation of complex mixtures in microscale devices is proposed. Unlike in free-flow electrophoresis devices, no mechanical pumping is requiredboth fluid transport and separation are driven electrokinetically. This gives the method great potential for on-a-chip integration in multistep analytical systems. The method enables us to collect fractionated sample and tensfold purification is possible. The model of the operation is presented and a detailed description of the optimal conditions for performing purification is given. The chip devices with 10-μm-deep separation chamber of 1.5 mm × 4 mm in size were fabricated in glass. A standard microchip electrophoresis setup was used. Continuous separation of rhodamine B, rhodamine 6G, and fluorescein was accomplished. Purification was demonstrated on a mixture containing rhodamine B and fluorescein, and the recovery of both fractions was achieved. The results show the feasibility of the method.