Assessment of Potassium Zinc Ferrocyanide as an Alkali-Metal Ion-Exchanger in Ion-Selective Electrodes

Abstract
Silicone rubber membranes containing potassium zinc ferrocyanide have been assessed as ion-selective electrode sensors for the determination of alkali metal ions. The slope of the calibration graph for potassium ion is 59 mV per decade change in concentration within the concentration range 5 × 10−4 to 10−1 M at 25°C. Selectivity constants (KK + /M+)are 9. 5, Cs+; 3. 3, Rb+; 0. 025, Na+; 0. 003, Li+; and 1.8, NH4 +, calculated from potential data obtained at 10−1 M concentrations of each ion separately. Similar membranes prepared from PVC responded similarly with a slight improvement in selectivity.