Interactions of mono‐ and divalent counterions with alkali‐ and enzyme‐deesterified pectins in salt‐free solutions

Abstract

The free fractions of monovalent and divalent counterions were determined on salt‐free solutions of pectins. The effects of charge density, distribution of the carboxyl groups, polymer concentration, and the nature of the counterion were investigated by determinating the calcium and sodium activity coefficients (with specific electrodes) and by measuring the transport parameters (by conductimetry). Poor agreement for calcium ions was found with the Manning theory. The strong binding of these ions to highly charged polymers, which is ascribed to a dimerization process was demonstrated in very dilute solutions.