Metal Oxide/Metal pH Sensor: Effect of Anions on pH Measurements

The electrochemical growth of iridium oxide on iridium (IrOx/ Ir) electrodes for use as pH sensors was examined. Usefulness of the electrodes was evaluated in a variety of solutions with anions of various oxy-sulfur species. IrOx/Ir electrodes were prepared, calibrated, and tested in sulfate-, sulfite-, bisulfite-, and thiosulfate-containing solutions of various concentrations. There were no serious effects of sulfate and sulfite ions on pH measurements by IrOx/Ir electrodes. After exposure to solutions with bisulfite and thiosulfate ions, considerable changes in calibration of the electrodes were observed, however.