Voltammetric and Potentiometric Behavior of 2-Pyridinethiol, 2-Mercaptoethanol and Sulfide at Iron(II) Phtalocyanine Modified Carbon-Paste Electrode

A carbon-past electrode modified with iron(II) phathalocyanine (FePc) was used as a sensitive potentiometric sensor for determination of 2-pyridinethiol (2PT). 2-mercaptoethanol (2ME) and sulfide ion in aqueous solutions. The modified electrode acts as an electrocatalyst for oxidation of these compounds, and lowers the overpotential for oxidation reactions by more than 400 mV, compared to the unmodified electrode. The process was dependent on the pH of the supporting electrolyte. The fast rate of electron transfer results in a near-Nernstian behavior of the modified electrode, and makes it a suitable potentiometric sensor for measurement of these compounds. Calibration studies were performed using potentiometry in oxygen or air saturated stirred solutions; linear responses were obtained over the range of about 1´10-6 to 5´10-3 M (correlation coefficients, r, of ~0.999, n=8). The modified electrode exhibited a fast response time (< 20 s), good stability, and has an extended lifetime; the standard deviation of slopes, during a period of two months, was 1.7-2.4% (n=10). Appropriate electrochemical and analytical data are presented.