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Stability and Lifetime of Potassium Solid-Contact Ion Selective Electrodes for Continuous and Autonomous Measurements



The current generation of solid-contact ion-selective electrodes (SC-ISE) suffer from lack of stability and lifetime. When using such sensors for remote, continuous, or autonomous measurements, these analytical characteristics are especially critical. In this work we compare several different configurations of ISEs to be deployed for monitoring in extreme environments, and present a novel configuration to improve performance. In particular we compare a polymeric hydrogel-based ISE, used previously in the Wet Chemistry Lab on the Phoenix Mars Lander, with three variations of solid supported nanoporous carbon-based ISEs. The symmetric membrane (SM) solid contact ISE (SM-SC-ISE) shows promise in overcoming many of the analytical problems encountered with hydrogel and solid-state devices. The results indicate that sensors based on the SM configuration provide improvements in both stability, and most importantly reproducibility, over other existing SC-ISEs. Future work will continue testing the SM configuration for use in a variety of extreme environments, including continuous monitoring and in-situ analyses in extraterrestrial environments.