# Intermediate-Layer-Free Solid-Contact Ion-Selective Electrodes on Gold Microelectrode Arrays: A New Approach for Stable and Reproducible Potentials

## TL;DR

This paper introduces a new type of ion-selective electrode using gold microelectrode arrays that eliminates the need for an intermediate layer while maintaining stable and reproducible performance.

## Contribution

The novel use of gold microelectrode arrays as a solid-contact ion-selective electrode without an intermediate layer is presented.

## Key findings

- Electrodes based on gold microelectrode arrays showed excellent stability, reversibility, and repeatability.
- The new approach simplifies sensor preparation while maintaining good analytical performance.
- The method was tested on potassium and nitrate ion-sensitive membranes with consistent results.

## Abstract

A new universal construction of intermediate-layer-free solid-contact ion-selective electrodes using a novel inner electrode, namely microelectrodes array composed of a large number of individual microelectrodes, was developed. This approach eliminates the need for a conventional solid-contact intermediate layer while maintaining excellent electrochemical performance. The studies were performed on two membrane model systems: potassium-ion-sensitive membranes based on valinomycin and nitrate-ion-sensitive membranes based on tridodecyldimethylammonium nitrate. In both cases, the membrane was applied directly onto the surface of the electrode substrate. The obtained results with such an ion-selective electrode based on a gold microelectrode array (GMA), a glassy carbon electrode (GCE), and a gold electrode (GE) were compared. It has been proven that, despite the lack of solid contact, whether in the form of an intermediate layer or as an addition directly to the membrane, ion-selective electrodes based on gold microelectrode arrays were characterized by very good analytical parameters. For those electrodes, a notable improvement in stability, reversibility, and repeatability of the electrode potential was observed and compared with electrodes using a glassy carbon disc electrode or a gold disc electrode as the electrode substrate. Thanks to the use of such an innovative electrode substrate, the final sensor preparation is shortened and simplified while maintaining good performance and stable readings.