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

Different carbon paste electrodes (CPEs) were investigated for their a bility to act directly as supports for mercury films formed ''in situ' ' by electrodeposition. A CPE, containing tricresyl phosphate as a pas ting liquid, was found to be especially suitable for this purpose. The mercury film on this support exhibited a more negative potential limi t than mercury films deposited onto common carbon pastes or glassy car bon. Thus, the mercury film electrode (MFE) with the tricresyl phospha te-based carbon paste support proved to be advantageous for differenti al pulse anodic stripping voltammetry (DPASV) of Zn(II). The effects o f various supporting electrolytes and nf the concentration of Hg(II) i ons on the response of zinc, were studied in detail together with an o ptimization of voltammetric parameters. Interferences from metal ions such as Ni(II), Co(II), Mn(II), and Cu(II), were also investigated. Fo r quantitative evaluations, Zn(II) was accumulated from a 0.1 M ammoni a buffer containing 2 x 10(-5) M Hg(II), a with an accumulation potent ial 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 d etection limit of 1 x 10(-) mol/L (accumulation time 180 seconds). The method was applied to the determination of Zn(II) in drinking water a nd deionized water.