A Gibbs-Donnan-based interpretation of the effect of medium counterion concentration levels on the acid dissociation properties of alginic acid and chondroitin sulfate

Abstract The sensitivity of the acid dissociation equilibria of alginic acid and chondroitin sulfate to changes in the counterion concentration levels of their aqueous solutions has, on the basis of earlier detailed studies of linear weak-acid polyelectrolytes and their crosslinked gel analogs, been attributed to the development of a counterion-concentrating solvent sheath circumscribing the surface of each charged molecule. A Gibbs-Donnan based approach to the use of this model has, as in the earlier studies, facilitated a meaningful and useful interpretation of this sensitivity. Estimates of solvent uptake by these hypothetical, counterion-concentrating regions of the alginic acid and the chondroitin sulfate, during their neutralization with standard base, have been resolved through use of this approach and yield insight with respect to their conformational properties.