MORPHOLOGY OF MICROPOROUS NEOSEPTA ION-EXCHANGE MEMBRANES AND ITS EFFECT ON SEPARATION OF BIOLOGICAL MIXTURES

Specially prepared microporous Neosepta ion-exchange membranes were in vestigated to establish a correlation between their structural charact eristics (pore-size distribution, porosity) and permeability to compon ents of immunoglobulin (Ig) fractions of mouse ascitic fluids. The sol utions to be separated contained IgG(1) with specificity to horseradis h peroxidase or to the heavy chain of human IgM, some other proteins, and a large amount of ammonium sulfate (0.22-0.35 M). Analysis of the membrane morphology carried out by scanning electron microscopy and me rcury porosimetry showed that the membranes possess a polymodal pore-s ize distribution. There are large open pores (400-600 and 200-300 nm i n diameter) on the membrane surfaces, but the void volume of the membr anes is a system of connected pores of smaller diameters (from 60-100 to 7-10 nm). The main part of the pores in the membranes displaying th e best separation ability was 8-17 nm in diameter. It was found that h ighly porous charged membranes (relative porosity 58-60%) with low ion -exchange capacity (0.02-0.1 meq/g) made it possible to achieve the de sired desalination degree of protein mixture (80-83%) within 5-7 h ins tead of 5 days needed in the traditional dialysis. Moreover, the amoun t of separated accompanying proteins reached 25-30% depending on membr ane porosity and the quality of specific IgG(1) was considerably impro ved. (C) 1995 John Wiley & Sons, Inc.