Electrophoretic control of concentration polarization in membrane plasmapheresis.

Membrane plasmapheresis is the separation of plasma from whole blood using microfiltration membranes. A major operating problem of membrane plasmapheresis is concentration polarization, the buildup of retained cells or solutes on the membrane surface. In this study, an electric field was used to control concentration polarization by transporting the negatively charged cells and solutes away from the membrane surface. Plasma flux and protein concentrations were measured before and after an electric field was applied. The electric field strength ranged from 0.32 to 1.50 V/cm, and the process conditions of blood hematocrit, transmembrane pressure drop, and average shear rate at the membrane surface were kept constant at 30%, 63.5 mm Hg, and 550 s-1, respectively. The plasma flux increased (10-50%) linearly with the increases in electric field strength, but the plasma protein concentrations in the ultrafiltrate decreased. The electric field dispersed the concentration polarization layer only enough to allow solvent (electrolytes and water) to pass, thus diluting the plasma and decreasing the protein concentration.