A Mercury-Free Thick-Film Graphite Electrode for Determining Cobalt in Natural and Potable Waters by Stripping Voltammetry

A mercury-free thick-film graphite electrode is proposed for determining cobalt(II) by stripping voltammetry. It was found that nitroso-R-salt ensures the highest efficiency of the preconcentration and determination of cobalt(II), as compared to the other organic reagents. The effects of different parameters (the pH of the solution, the concentration of organic reagents, the potential and duration of preconcentration, potential sweep rate, and interfering elements) were studied to select the optimum conditions for determining cobalt(II) at a mercury-free thick-film graphite electrode. The detection limit for cobalt(II) was 7.3 × 10^–12 M (or 0.4 ng/L) for a preconcentration time of 30 s. A procedure for determining cobalt(II) in potable and natural waters was developed and certified (certificate no. 224.01.10.002/2004, Ural Scientific Research Institute of Metrology).