Determination of Relative Counterion Binding Constant to Cationic Micelles

The efficiency of counterion affinity towards ionic micelles is often described in terms of the degree of counterion binding ( β X ) to ionic micelles or the conventional ion-exchange constant ( K X Br ) or relative binding constant ( R X Br ) of X − and Br − counterions. This review describes the use of ionized phenyl salicylate ions, PSa − , as a new probe to determine K X Br values using a semiempirical spectrophotometric method. The value of K X Br is found to be comparable to reported values obtained using different probes by the semiempirical kinetic method as well as different physical methods. Application of semiempirical methods for calculation of K X Br or R X Br values involves an inherent assumption that these values are independent of the physicochemical characteristics of the probe molecule.