Bypassed ion-selective electrodes – self-powered polarization for tailoring of sensor performance
Potentiometric ion-selective sensors are attractive analytical tools as they have simple apparatus and facile use; however their analytical parameters cannot be easily tuned. To tailor the performance of these sensors, application of instrumental control – electrochemical trigger – is usually required. The proposed approach offers a self-powered instrument-free alternative. It benefits from a spontaneous redox process for the ion-selective electrode bypassed by a zinc wire and a resistor connected in series. Spontaneous oxidation of zinc induces charge flow and the accompanying reduction of the solid contact material of the sensor, magnitude of the current and finally the potential of the electrode can be controlled by adjusting the bypass resistance. The ultimate result of the proposed approach is qualitatively equivalent to recording sensor response under polarized electrode potentiometry conditions, however, it does not require application of a galvanostat. The change in the magnitude of the resistance connected can be used to tailor analytical parameters such as detection limit, linear response range, and selectivity of the sensor. As a model example, potassium-selective all-solid-state sensors with a polypyrrole solid contact were used.