Coulometric micro-titrator with a ruthenium dioxide pH-electrode Original Research Article

A coulometric diffusional titrator with a ruthenium dioxide pH-sensing electrode for the end-point detection in acid–base titrations is presented. The device was prepared by galvanic deposition of noble metals onto electrodes etched on a copper clad printed circuit board. Five electrodes were employed: three gold electrodes (two actuator and one counter) for the coulometric production of the titrating protons or hydroxide ions, and a RuO2-electrode and Ag/AgCl pseudo-reference electrode pair for the end-point detection. The RuO2-electrode for pH-measurements showed a linear response to the variation of the pH-value in the range from 2 to 12 pH-units and was useable for a period of 3 months. The device was found to yield linear relationships between the analyte concentration and the equivalence time for concentration ranges of acetic acid and ammonia between about 0.1 and 100 mM.