Mechanistic Studies on Crystal-Membrane Ion-Selective Electrodes

Abstract

The properties of several ion-selective electrodes having single-crystal, polycrystalline, and mixed-crystal membranes are examined. Measurements of the electrode impedance are used to derive equivalent circuit models of each type of electrode. The lanthanum fluoride electrode is shown to have a surface film resembling the hydrolyzed surface film on glass membrane electrodes. A distinction is made between electrodes in which ion transport occurs across the membrane and those in which ion-blocking is found at the electrode. All of the electrodes are found to exhibit nonlinear space charge effects. The resulting equivalent circuit models point the way to a possible means of measuring the kinetics of ion exchange at a membrane-solution interface. © 1970, American Chemical Society. All rights reserved.