Abstract
In this work, the pH sensor electrode based on iridium oxides (IrOx) was developed and applied to potentiometric titration, instead of the traditional glass membrane electrodes, with its dominant features such as easy-implementation, low-cost and small-size. The electrode consisting of the IrOx layered on the surface of titanium substrate was fabricated by an anodizing method. Such electrode (IrOx/Ti) was highly sensitive to a pH change in a solution, but not in the presence of oxidizing or reducing agents. With the aim to minimize these chemical interferences, the IrOx/Ti electrode was covered by a nafion thin-film via a dip-coating method, namely Nf-IrOx/Ti. Besides the high mechanical stability, the Nf-IrOx/Ti sensing electrode indicated a linear correlation between the potential and the solution pH in the range of pH 2(12, with the response time of 120 s for an equilibrium. Although the response time of such pH electrode was quite longer than those of IrOx/Ti (60 s) and the commercial glass membrane electrode (30 s), the Nf-IrOx/Ti electrode permitted determining the equivalence points in acid-base potentiometric titrations with a high accuracy (less than 1 % relative errors in comparison with the corresponding values obtained by the commercial glass membrane electrode).
