Characterization and application of a metallic tungsten electrode for potentiometric pH measurements

This study demonstrated the application of a metallic tungsten electrode for pH measurement. The metallic tungsten electrode exhibited an excellent linear response similar to the tungsten oxide electrode. Both the metallic tungsten electrode and tungsten oxide electrode used in our study exhibited a near-Nernstian response of −51.9 mV/pH and −56.8 mV/pH, respectively. No obvious interference was observed from the primary cations. The fitted curve for the metallic tungsten electrode showed a smaller slope (−1.87 mV/°C) and more linear (R2 = 0.999) temperature response than those of the tungsten oxide electrode, indicating its suitability in practical pH measurements due to its precise compensation of temperature. Moreover, the metallic tungsten electrode was almost uninfluenced by the hydrodynamic effect, and its open circuit potential change was less than 2 mV even at high stirrer rotation speeds (120 rev/min) in solution. Long-term stability could be achieved for the metallic tungsten electrode over the pH range 4.5–8.0. Owing to the advantages such as precise temperature compensation, insensitivity to the hydrodynamic effect, long-term stability, good selectivity, and intrinsic properties of the solid-state electrode, the metallic tungsten electrode has shown promise for long-term pH monitoring.