Application of a platinum sheet for pH measurement based on chronopotentiometry

In this study, a novel solid-state pH sensor based on an untreated platinum sheet was investigated. Chronopotentiometry using positive and negative currents was applied to effect the interconversion of Pt and PtO. To eliminate the influence of concentration polarization, a galvanostatic double-pulse method was applied for pH measurement. The consecutively applied currents were +100, +3, -100, and -3 mu,A for excitation times of 0.5, 1, 0.5, and 1 s, respectively. Stable potentials under the small currents were obtained which could be used to determine pH. The platinum sheet electrode exhibited near-Nernstian behavior in the pH range 2-12, with fitted lines having slopes of -44.2 and -51.1 mV/pH unit under the positive and negative currents, respectively. Overall, excellent linearity and reproducibility could be achieved. Moreover, the temperature responses for the method in pH 4, 6.86, and 9.18 buffer solutions obeyed the Nernst equation, and further supported the proposed mechanism for pH determination. In conclusion, this new detection method provides a solid-state, long-lived, and adaptable solution for pH measurement. (C) 2015 Elsevier B.V. All rights reserved.