WATER FLUX ACROSS NEUTRAL CARRIER MEMBRANES

We investigated the water flux through neutral carrier membranes cause d by the osmotic pressure difference of the solutions on both sides of these membranes. Miniaturized thin-film ion-selective electrodes were used as their extremely small internal electrolyte volume as well as their extremely thin membrane make them specifically suitable for such studies. The dilution of the internal electrolyte due to the transmem brane water nux results in a significant shift of the ISE potentials. A model explaining the potential versus time curve of thin-film sensor s was developed. The penetration coefficient of water is determined ex perimentally with respect to the lipophilicity of the membrane plastic izer used. The inverse of the square root of the penetration coefficie nt depends linearly on the logarithm of the lipophilicity for almost a ll investigated membranes.