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 (beta X) to ionic micelles or the conventional ion-exchange constant (K-Br (X)) 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-Br (X) 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.