Micromolar determination of sulfur oxoanions and sulfide at a renewable sol-gel carbon ceramic electrode modified with nickel powder

The sol-gel technique was used to fabricate nickel powder carbon composite electrode (CCE). The nickel powder successfully used to deposit NiOx thin film on conductive carbon ceramic electrode for large surface area catalytic application. Repetitive cycling in potential range -0.2 to 1.0 V was used to form of a thin nickel oxide film on the surface carbon composite electrode. The thin film exhibits an excellent electro-catalytic activity for oxidation of SO32- S2O42-, S2O32-, S4O62-, in alkaline pH range 10-14. Optimum pH values for detection of all sulfur derivatives is 13 and catalytic rate constants are in range 2.4 x 10(3)-8.9 x 10(3) M-1 s(-1). The hydrodynamic amperometry at rotating modified CCE at constant potential versus reference electrode was used for detection of sulfur derivatives. Under optimized conditions the calibration plots are linear in the concentration range 10 mu M-15 mM and detection limit 1.2-34 mu M and 0.53-7.58 nA/mu M (sensitivity) for electrode surface area 0.0314 cm(2). The nickel powder doped modified carbon ceramic electrode shows good reproducibility, a short response time (2.0 s), remarkable long term stability, less expense, simplicity of preparation, good chemical and mechanical stability, and especially good surface renewability by simple mechanical polishing and repetitive potential cycling. This sensor can be used into the design of a simple and cheap chromatographic amperometry detector for analysis of sulfur derivatives. (c) 2005 Elsevier Ltd. All rights reserved.