CAPACITOR THEORY FOR NONFARADAIC POTENTIOMETRY

The generally accepted ion-exchange theory fails to explain the origin of the membrane electrode potential. The newly proposed capacitor theory emphasizes the importance of the electrode surface, the double layer, the adsorption of both cations and anions on the zwitterionic surfaces, the surface active sites, the charge density, the role of anions, etc. Both theoretical treatment and experimental results are presented to support the capacitor theory. The membrane electrode is a capacitor, not a cell that requires redox reactions. Reasons for the past misuse of the Nernst equation are given. Acid and alkaline errors; suspension effects; charging, discharging, and recharging processes; chemical potential amplification; and solid-state membrane electrode devices are discussed. The basic and correct concepts for understanding mechanisms are stressed. © 1990.