Equilibrium potential of potentiometric ion sensors under steady-state current by using current-reversal chronopotentiometry

Potentiometric ion sensors based on a solvent polymeric ion-sensing membrane and a conducting polymer as the solid contact were investigated by current-reversal chronopotentiometry. The low-frequency electrochemical behavior of the electrodes resembles a series RC equivalent circuit. The resistance R was attributed primarily to the bulk resistance of the ion-sensing membrane and the capacitance C was attributed to the bulk redox capacitance of the conducting polymer layer acting as an ion-to-electron transducer. It is shown that the equilibrium potential of the ion sensors can be obtained in the presence of a steady-state current by using current-reversal chronopotentiometry (double current step chronopotentiometry).