Influence of the nature of the support on the temperature ehaviour of "all-solid-state" PVC membrane nitrate ISEs

Abstract

PVC membrane nitrate ion-selective electrodes based on the tetra-n-octylammonium nitrate/di-butylphthalate system, with the membrane applied to a silver disk ("type A"),or to supports made of conductive epoxies of four different types (gold-, silver-, copper- or graphite-loaded) ("type B/X", where X is the loading element of the epoxy), and, for comparison, with internal solution ("type C"), were studied in parallel to investigate how the nature of the support material influences their response characteristics and the effect of temperature (range 10-70°C) on these. It was found that type B/Ag and type C electrodes exhibited close to thermodynamic behaviour up to 70° C and the remaining electrodes up to 60° C. The electrode of type B/C showed an isopotential point concentration of ca. 10- M, while all the other all-solid-state electrodes had values ranging from 3 to 28 M. Calibrations under nitrogen and E vs. time measurements when the atmosphere was changed from air to nitrogen and back showed that for electrodes of types A, B/Ag and C the response is not sensitive to the oxygen partial pressure, near Nernstian slopes being maintained even under nitrogen, while electrodes of types C/C, C/Cu and C/Au show lower slopes under nitrogen. The overall results show that the nature of the support material influences the response characteristics of the PVC membrane and therefore these can be improved by a trial-and-error selection of the support. © 1990.