Modified composite electrode containing HgO as built-in mercury precursor for anodic stripping analysis of trace metals

A HgO-modified composite electrode was prepared by adapting a composite electrode technique, which is compatible to a mercury thin-film electrode in anodic stripping analysis of heavy metals. The preparation method and utilization of the HgO-modified composite electrode in anodic stripping analysis are described. The built-in mercury precursor HgO could be utilized feasibly for generation of surface mercury droplets by in situ electrochemical treatment or pretreatment without the necessity of a Hg(2+) solution. Mercury microdroplets generated on the electrode surface were stable to meet ordinary requirements for stirring of solution or rotation of electrode. Hydrogen gas evolution perturbed the stability of the surface mercury severely. The hydrogen reduction overpotential was directly dependent on the content of mercury oxide in the electrode matrix. The electrodes containing more than 10 wt % mercury oxide were fairly stable so that the deposition potential could be extended up to -1.2 V for most applications. The electrode revealed improved renewability and stability of surface mercury as well as reproducibility of analysis. The convenience of voltammetric analysis will be greatly improved if this electrode technique is applied in conjunction with a fast scanning stripping technique, in which the deoxygenating step may be skipped. Application of this electrode technique is very promising for environmental or industrial field analysis because of its simplicity of treatments.