EXPERIMENTAL IN-SITU MEASUREMENT OF CONCENTRATION POLARIZATION DURINGULTRA-FILTRATION AND MICRO-FILTRATION OF BOVINE SERUM-ALBUMIN AND DEXTRAN-BLUE SOLUTIONS

Concentration polarisation arising during the filtration of bovine ser um albumin (BSA) and Dextran Blue is studied by two non-intrusive tech niques. The first technique, which measures overall layer build up, is a further development of a radio isotope technique previously introdu ced. The second technique uses a micro-array of semiconductor photosit es to measure infrared absorption of species in the polarised layer. T he development of the polarised region is observed as a function of di stance perpendicular to the membrane surface. The experiments with the radio isotope labelled proteins using different pore size membranes d emonstrated that there is a large similarity between filtration with d ifferent pore size membranes - from microfiltration to ultrafiltration . The amount of solute retained dynamically above the membrane is with in half an order of magnitude, over pore sizes differing by 2 orders o f magnitude. The directly observed concentration polarisation profiles followed generally expected trends, and demonstrated the large solute concentrations that exist near the membrane surface.