SILVER ION SENSORS BASED ON AG-AS-SE-TE GLASSES .1. IONIC SENSITIVITY AND BULK MEMBRANE-TRANSPORT

AgAsSeTe glasses have been used as membranes of silver ion-selective electrodes. Sensors based on ion-conducting glasses with low tellurium content display high Ag+ ion sensitivity, potential stability and reproducibility. They are superior to crystalline silver-ion sensors in selectivity in the presence of interfering ions, such as mercury(II), iron(III) and copper(II) ions. Semiconducting Te-rich glasses show some features in silver ion response (super-Nernstian slope in diluted solutions, less stable potentials, etc.) that are explained by competitive redox processes at the glass/solution interface. Deterioration of the response is related both to increases in electronic conductivity and to decreases in ionic conductivity. A lack of chemical stability of the surface of Te-rich glasses can also play a certain role. © 1990.