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 -3 M 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 15 s in the same order in both solvents. The change in the electrode potential from the acidic to basic region was 375 to -75 mV in γ-butyrolactone and 394 to 6 mV in propylene carbonate. The determination of 25-30 mg 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 109 mV. © 2012 Elsevier Ltd. All rights reserved.