Effect of polyelectrolytes on diffusion of ionizable species through polymer membranes.

Permeability data were obtained from the diffusion of sodium, potassium, calcium and iron (ferric) through regenerated cellulose and silicone rubber. Measurements of intestinal uptake and transport of zinc and iron (ferric) was determined across an everted segment of rats' small intestine. The effect of an ionic exchange resin on the diffusion of these cations was measured. Correlations were established between a specific amount of the resin and the diffusion or absorption of the cations and the charge on the cation. The effect of the resin on the diffusion of the cations through regenerated cellulose was an increase in the diffusion as the charge on the cation increased. These increases ranged from 1.6 to 2.82 times the diffusion coefficient, where the resin was present, as compared to the diffusion coefficient where no resin was present. Membrane activation energies were computed for the cations by measuring the variation in permeation rate through regenerated cellophane at different temperatures with and without the resin. Correspondingly decreased magnitudes of activation energies ranging by factors of 0.61 to 0.87 were found when the resin was present. Equilibrium states were measured for each cation using varing amounts of the resin. A calculated to measured equilibrium comparison was in good agreement. Correlations between the calculated diffusion coefficient obtained from the diffusion of the cations through silicone rubber, with and without the resin, were found to depend upon the charge and number of waters of hydration for each cation. These increases ranged from 1.11 to 3.06 times the diffusion coefficient as a result of the resin. Solubilities of each cation in the rubber were determined and found to be temperature dependent. Decreasing magnitudes of activation energies ranged by factors of 0.91 to 0.57 when the resin was present. Correlations were established between the measured activation energies and reported free energy change for the hydration of each cation. Zinc and iron (ferric) intake and transport were measured across everted segments of rat small intestine using and in vitro procedure. The presence of the exchange resin resulted in a slight decrease in the intestinal uptake of the zinc while increasing the transport of the metal across the intestinal wall by a factor of 1.89 times. Both uptake and transport of the iron was decreased by the resin by a factor of 1.65 times.