Comparison of Polypyrrole-Conducting Polymer and Ag/AgCl Reference Electrodes Used for Ruthenium Dioxide pH Electrode

A laboratory-made conducting polymer reference electrode (CPRE) was developed using polypyrrole coated onto indium tin oxide by the electroplating technique and used as the miniaturized reference electrode (RE) for a ruthenium dioxide ion-selective electrode device in electrochemical hydrogen ion measurements. Ruthenium dioxide thin films were deposited by a radio frequency sputtering method, and the sensing characteristics of were measured with a CPRE and an Ag/AgCl RE. Subsequently, the selectivity coefficients ( , , , , and ) of the ruthenium dioxide thin film with the CPRE were investigated. Furthermore, we also compared the sensing characteristics (such as: pH sensitivity, drift rate, hysteresis width, and response time) of the thin-film pH electrode with a commercial Ag/AgCl RE and the laboratory-made CPRE. The experimental results demonstrated that the sensing characteristics of the pH electrode measured with the laboratory-made CPRE are superior to the Ag/AgCl RE, and the size of the CPRE can be efficiently miniaturized compared to a commercial Ag/AgCl RE.