Potentiometric selectivity and impedance characteristics of a NASICON-based ion selective electrode

The potentiometric response of the Na+ ion selective electrode based on NAS ICON (Na3Zr2Si2PO12) as well as the impedance of the NASICON/solution inter face have been measured in NaCl. LiCl and KCI aqueous solutions. The behavi or of the NASICON was successfully explained on the basis of the Eisenman m odel which involves an ion exchange process between the membrane and the so lution. The apparent ion-exchange densities and potentiometric selectivity coefficients of the NASICON membrane have been determined for Na+, Li+ and K+ ions. The higher the apparent standard ion-exchange current density is, the better is the selectivity. However, no simple relationship can be estab lished between these two parameters. (C) 1999 Elsevier Science Ltd. All rig hts reserved.