VOLTAMMETRIC INVESTIGATIONS ON CARBON-PASTE ELECTRODES AS SUPPORTS FOR MERCURY FILMS

Different carbon paste electrodes (CPEs) were investigated for their ability to act directly as supports for mercury films formed ''in situ'' by electrodeposition. A CPE, containing tricresyl phosphate as a pasting liquid, was found to be especially suitable for this purpose. The mercury film on this support exhibited a more negative potential limit than mercury films deposited onto common carbon pastes or glassy carbon. Thus, the mercury film electrode (MFE) with the tricresyl phosphate-based carbon paste support proved to be advantageous for differential pulse anodic stripping voltammetry (DPASV) of Zn(II). The effects of various supporting electrolytes and nf the concentration of Hg(II) ions on the response of zinc, were studied in detail together with an optimization of voltammetric parameters. Interferences from metal ions such as Ni(II), Co(II), Mn(II), and Cu(II), were also investigated. For quantitative evaluations, Zn(II) was accumulated from a 0.1 M ammonia buffer containing 2 x 10(-5) M Hg(II), a with an accumulation potential of -1.5 V (vs. Ag/AgCl). The current response of Zn(II) was linear for a concentration range from 2 x 10(-) to 2 x 10(-5) mol/L with a detection limit of 1 x 10(-) mol/L (accumulation time 180 seconds). The method was applied to the determination of Zn(II) in drinking water and deionized water.