Noble Metal Oxides Electrodes and Analytical Application Thereof for Acid-Base Titrations in Non-Aqueous Solvents

Abstract

Electrochemical characterization of palladium and platinum oxide electrodes is reported. Palladium (platinum) oxide layer has been formed by thermal oxidation of smooth Pd(Pt) electrode. The palladium/palladium oxide electrode enables fast measurements, with good sensitivity of 54 ± 0.9 mV per decade, in acidic and base solutions (linear range of response up to the concentration 1 × 10−6 M) in acetonitrile and 49 ± 1.2 mV per decade in propionitrile. The response of the platinum/platinum oxide was linear in the concentration range between 5 × 10−2 and 1 × 10−6 M, and a sensitivity of 52 ± 1.6 mV per decade in acetonitrile was obtained. The response time of the electrodes was less than 15 s in the both solvents. The properties of the palladium oxide electrode were similar to those of the platinum one. Some potential analytical applications of the sensors are pointed. Palladium and platinum oxide electrodes for the potentiometric titrations of acids (benzoic, anthranilic, salicylic acids, and sulfadiazine) and bases (N,N′-diphenylguanidine, tributylamine, and collidine) in acetonitrile and propionitrile were studied. Potassium hydroxide, tetrabutylammonium hydroxide and perchloric acid proved to be very suitable titrating agents for these titrations. The standard deviation of the determination of the investigated acids and bases was less than 0.7% from those obtained with a glass electrode. The electrodes have the following advantages: fast response, and reproducibility, the service life is long and without considerable divergence in potentials, the manufacture is simple, the production cost is low.