MEMBRANE MODEL FOR NEUTRAL-CARRIER-BASED MEMBRANE ELECTRODES CONTAINING IONIC SITES

The selectivity characteristics of neutral-carrier-based electrodes can be improved to a large extent by the optimization of the ionic sites/carriers ratio. A new membrane model and a new equation for the emf response of such membranes are introduced. They illustrate the dependence of the emf response on the activity of free carriers available. As a case of practical importance the emf function of a magnesium ion-selective electrode is discussed. It demonstrates that the emf function normally deviates from the Nikolsky-type behavior and that transient potentials and long-term drifts occur and therefore make the selectivity determination according to the separate solution method questionable. The measured data are in good agreement with the values calculated on the basis of the reported model.