Solid state iridium oxide-titanium based sensor for flow injection pH measurements

Iridium oxide-coated titanium wire is prepared by controlled electrodeposition (current density 5 mA/cm² for 10 min) and used as a solid state pH sensor. The sensor is sensitive for pH variations over the range 2-10 with calibration slopes of ∼ 65.5 and 59.1 mV/pH unit under static and hydrodynamic modes of operation, respectively. The general performance characteristics of the sensor are similar to those of the glass electrode for direct pH monitoring of solutions. The sensor exhibits reasonable stability (±0.005 pH), reproducibility (±2%) and fast response time (20-30 s). The method of preparation is simple, utilizes an inexpensive titanium metal substrate and offers the possibility of fabrication of sensors with various geometry and/or of micro and ultramicro sizes usable for flow injection analysis. No interferences are caused by alkali and alkaline earth metal cations and various anions at level ≥ 10⁴ molar excess over H⁺.