Studying Ion Exchange Capacity Distribution in Charged Membranes by Means of Autoradiographic Techniques

A new method for studying ion-exchange capacity in charged membranes is proposed, which is based on a special application of the autoradiographic technique. It consists of equilibrating membrane samples, under suitable experimental conditions, with solutions of NaCl containing small amounts of the 22Na radioisotope, and then exposing photographic emulsions to the ionizing radiation of the so-treated samples, in order to obtain pictures of sodium ion distribution inside the membrane. For testing method reliability, samples of a perfluorinated ionomer membrane were used. A few examples which can summarize the main features of applying autoradiography to ion-exchange membrane studies are presented and discussed.