CONCENTRATION AND CONCENTRATION GRADIENT MEASUREMENTS IN AN ULTRAFILTRATION CONCENTRATION POLARIZATION LAYER .1. A LASER-BASED REFRACTOMETRIC EXPERIMENTAL-TECHNIQUE

In this paper we report on the development of an automated, laser-base d refractometric technique for the measurement of concentration and co ncentration gradient in the concentration polarization layer during de ad-end ultrafiltration. Spatially and temporally resolved measurements can be made to within 200 mu m of the membrane. Solvent is pumped thr ough the layer at a constant flow rate, and the driving pressure is al so measured. The system was calibrated and tested using the biopolymer hyaluronan (M-n=434000; M-w=605000; M-z=827000). Good repeatability, accuracy, and sensitivity were demonstrated. These studies lay the fou ndation for a physico-chemical study of concentration polarization dyn amics, reported in a companion paper.