Evaluation of the zirconia pH sensor at 95° C

An yttria-stabilized zirconia electrode for measuring pH at elevated temperature and pressure has been described by Niedrach, who verified its response at 95°C in comparison with glass pH electrodes. The present paper reports studies at 95° C on zirconia tubes available from three different commercial sources. This study, conducted with conventional aqueous internal filling solution and conventional internal and external reference electrodes, was designed to obtain fundamental pH electrode parameters of slope, resistance, asymmetry potential, and time of response in standard buffers and known strength acids and bases. A coulometric experiment is reported to aid in assessing the efficiency of the zirconia electrode. Uncertain performance found in this evaluation may be attributed to chemical, physical, and surface problems in the commercially available zirconia tubes or to less than ideal pH response for zirconia membranes.