ELSEVIER Journal of Electroanalytical Chemistry 436 (1997) 119-125 Effects of pH on ion transport in weak amphoteric membranes

We have sludied Iheorelically Ihe efl¢cls o1 ' pH on Ihe ion Irausport lhrougll amphoteric polymer membranes compo~ed of we~,k polyeleclmlytes whel ~ the charged groups are randomly distributed along the axial direction of the membrane. This system serve ~ a ~ a simpliiied model fi~r the pH controlled ion Iraltspoll alld drug delivery through membranes of biological inlerest. The |heoretical pproach employed is based on the Nernst-Planck equations. The complete system of electrical charges formed by: (i) the pH de~nden|. amphoteric membrane fixed charge, and (it) the four mobil ~ charges (the two salt ions and the hydrogen and hydroxide ions) have been taken into account without any additional ssumption. The model predictions show that he ionic fluxes and the membrane potential re very sensitive to the external pH, and the po~, : ~tial utility of these predictions for the analysis of experiments involving pH dependent passive transport through membranes is emphasi~:ed. © 1997 Elsevier Science S.A. I(evword.~: Weak ampholeric membranes: Ion transport; El'feels of pH: Theore|ical modellin