Abstract: An apparatus for the performance of efficient, large scale separations, particularly electrophoresis and isoelectric focusing, in free solution is described. Inner and outer cylinders define an annular separation chamber for solutions stabilized against convective flow by Taylor vortices generated during rotation of inner cylinder above threshold frequencies. Separation substrates in solution migrate independently in a potential field established between axially distal anodic and cathodic regions of the annular chamber. Axially defined portions of fluid in the chamber identified to contain concentrations of selected substrates are readily separated from other portions of fluid in the chamber.