Voltammetric and potentiometric characterization of magnetite electrode for the assay of weak organic acids in non-aqueous media

Abstract

The construction and general performance characteristics of a novel potentiometric electrode responsives to hydrogen (lyonium/lyate) ions are described. This sensor is based on the use of the magnetite mineral as the working surface of the electrode. The sensor exhibits fast, stable and sub-Nernstian for the p-toluenesulphonic acid over the concentration range 1×10−1 to 1×10−3M at 25°C with slope of 39.3±0.6 and 41.0±0.5 per concentration decade in propylene carbonate and γ-butyrolactone, respectively. The response time is 13 and 15s in the same order in both solvents. The change in the electrode potential from the acidic to basic region was 375 to −75mV in γ-butyrolactone and 394 to 6mV in propylene carbonate. The determination of 25–30mg of some important organic acids (benzoic, anthranilic, and salicylic acid) in non-aqueous media shows an average recovery of 100.2% and 99.8% with relative standard deviation of 0.17–0.47% in both solvents. Potentiometric titrations of acids involving potassium hydroxide as titrant are monitored in both solvents with inflection point from 207 to 109mV.