Surfactantion-selective electrodes: A promising approach to the study of the aggregation of ionic surfactants in solution

Abstract

The potentiometric method based on surfactant ion-selective electrodes (SISEs) was broadly applied to ionic surfactants in solution due to the change in their activities, i.e., concentration in dilute solution, of both the counterions and ionic surfactants at the point of aggregation. The monomeric surfactant concentration can be determined by SISEs with almost no pretreatment, even if the sample solutions were colored or viscous. Ion-sensitive electrodes are usually used to investigate the dimerization, aggregation, and micelle formation of ionic surfactants in aqueous solution. By using SISEs, the binding isotherm of ionic surfactants bound to other materials such as polymers and biomolecules (DNA and proteins) can be calculated easily. According to the binding isotherms, the different binding and aggregation processes between ionic surfactants and other materials can be identified and characterized, which is important for understanding the interaction between ionic surfactants and polymers and/or biomolecules. Herein we present a comprehensive review of the literature devoted to SISEs used in the aggregation of surfactants in solution over the last two decades, looking back the developmental history of SISEs, reviewing the applications of SISEs in the studies of surfactant/surfactant mixtures, the adsorption of surfactants on polymers, including neutral polymers, polyelectrolytes, and biopolymers and the interactions between surfactants and lipid vesicles, etc., prospecting the new wave of SISEs.