Electrophoresis is a widely used analytical technique in the medical and biotechnology industries. It can provide for the determination of thousands of individual compounds on this small scale. The operating conditions are quite conducive to use with the delicate products of genetic engineering. Due to other complexities associated with scale-up, the process is not widely used on a large scale. A novel recycling electrophoretic instrument was investigated as a preparative protein separation device. The process occurs in a thin film of liquid between two flat plates, in a direction perpendicular to the flow. This device was unique in its use of a relatively high flowrate, and recycling of the process fluid as a method for increasing residence time. The apparatus was operated in three modes, isoelectric focusing (IEF), zone electrophoresis (ZE) and isotachophoresis (ITP). For use in the ITP mode, a computer was used for data acquisition and control functions. Model systems included monoclonal antibodies and lentil lectins.