Electrochemical Characterization and Application of Ni-RuO2 as a pH Sensor for Determination of Petroleum Oil Acid Number
R. Karimi Shervedani*, H.R. Zare Mehrdjardi and S.H. Kazemi Ghahfarokhi
Department of Chemistry, University of Isfahan, Isfahan 81746-73441, I.R. Iran
(Received 4 June 2006, Accepted 29 December 2006)
Electrochemical characterization and application of nickel ruthenium dioxide (Ni-RuO2) as a pH sensor for the determination of petroleum oil acid number is described. The sensor consists of RuCl3 thermally decomposed onto the upper side of a polycrystalline nickel electrode at 400 °C in an open furnace. The advantages of the sensor are: (i) easy preparation, (ii) fast response in a large pH range, (iii) high physical and chemical stability, and (iv) excellent reproducibility as determined by the reproducible linear variation of charge transfer resistance (Rct) as a function of overpotential (h ) obtained by electrochemical impedance spectroscopy (EIS), and the Nernstian slope of the electrode potential in a wide range of pH (1.5-12.5) obtained by potentiometric measurements. The potentiometric selectivity coefficients of the sensor toward some anions and cations were evaluated in aqueous solution. The characterized Ni-RuO2 pH sensor was successfully tested for the determination of petroleum oil acid number.
Keywords: pH sensor, Ni-RuO2, Acid number, Ruthenium dioxide, Petroleum oil