Simultaneous Determination of Nickel and Cobalt in Natural Water and Sediment Samples on an in-situ Plated Mercury Film Electrode by Adsorptive Cathodic Stripping Voltammetry

the reliable determination of trace and ultra-trace concentrations of nickel and cobalt.1–10 In particular, adsorptive cathodic stripping voltammetry, which utilizes a suitable complexing agent to enhance the electrode behavior of both metals, is considered to be one of the most sensitive methods for their determination. The range of complexing agents that has been employed for this purpose includes 2,2′-bipyridine, dimethylglyoxime, 1-(2-pyridylazo)-2,7-dihydroxynaphthalene and noxime. Of these, the use of dimethylglyoxime (DMG) has gained wider use for the adsorptive voltammetric determination of ultra-trace concentrations of nickel and cobalt in various sample materials. Most of the determinations of nickel and cobalt by adsorptive cathodic stripping voltammetry (AdCSV) to date has been based on the use of a hanging mercury drop electrode.3–10 In recent years, the use of a mercury film electrode11–14 has been reported for either individual or simultaneous determinations of nickel and cobalt. The simultaneous determination of both metals by AdCSV on a mercury film electrode was reported by Economou et al.11 This method involves the use of an ex-situ plated mercury film for simultaneous determination of Ni and Co by square-wave adsorptive stripping voltammetry. The extra step created by the ex-situ plating of mercury film and other associated limitations reported in that paper has not attracted much interest in this method. However, it may be possible to attract more interest in this approach if a simpler method involving in-situ plating of mercury is available, as has been demonstrated by the current wide use of anodic stripping voltammetry on in-situ plated mercury film electrodes. Furthermore, the use of an in-situ plated mercury film electrode will enable simpler operation and will provide greater opportunity for automation of the technique. In this paper, we discuss the suitability of an in-situ plated mercury film on a glassy carbon electrode for the simultaneous determination of trace and ultra-trace concentrations of nickel and cobalt, investigated by AdCSV. Also, the use of a mercury-plated electrode for a reliable AdCSV determination of these metals in water and sediment samples is considered.