A surface renewable iridium oxide-glass composite hydrogen ion electrode

A robust and surface renewable iridium oxide-based pH glass composite electrode was prepared by modifying glass matrix with iridium oxide particles. Fine glass powder coated with iridium oxide was prepared by pyrolyzing ammonium hexachloroiridate-coated glass powder under oxygen atmosphere. First the glass powder was molded into a disk, by using a press, then was sintered in high temperature, and was finally fabricated. The electrode showed linear response between pH 1 and 13 with close slopes to the theoretical value, − 59.2 mV/pH. The electrode showed low hysteresis upon sudden changes of pH from 2 to 6, but in extreme conditions, from pH 13 to 1, it showed values near 16 mV. The electrode maintained the pH response for 36 days, without a significant slope drift, in various storage conditions — deionized water, a pH 7 buffer solution, 4 M KCl, and even in the air. Most of the cations and anions, except electrochemically active compounds or ions, did not interfere with the electrodes seriously. The electrode surface can be renewed reproducibly, by a simple grinding process whenever it becomes fouled or deactivated. The electrode matrix was durable and showed extended lifetime although it was ground repeatedly with 2000 grit SiC emery paper for surface renewal.