Theory of the Transient Potential Response of Ion-Selective Electrodes Based on the Polarizable Oil/ Water Interface

Abstract

The theory of the transient potential response of potentiometric ion-selective electrodes (J. Electroanal. Chem. Interfacial Electrochem., 378, 215 (1994)) is further elucidated. General solutions of the transient potential vs. time curves for a stepwise change in the activity (concentration) of a potential-determining ion in an external solution were numerically obtained for different cases concerning their ion-transfer kinetics. Also, the response time, defined as the time which is taken by the potential of an ion-selective electrode to change from its initial value to within a given limit of the final value, was numerically obtained, and is discussed in terms of the ion concentrations, the kinetic parameters of the ion-transfer reaction, and the electrical double layer capacity of the ion-selective electrode interface. Furthermore, the theory is extended so as to include the transient potential response of neutral-carrier-based ion-selective electrodes. The theory predicts the effect of the concentration of a neutral-carrier, which depends on the reaction mechanism of the carrier-assisted ion transfer across the interface.