Sammendrag
The development of home-made bare gold-disk microelectrodes of 25 and 125-µm has permitted to carry out measurements of trace metals in natural waters using voltammetric procedures. In filtered seawater samples, square wave anodic stripping voltammetry (SWASV) with a frequency of 25Hz is applied for analysis. On the contrary, on unfiltered contaminated river samples, differential pulse anodic stripping voltammetry (DPASV) gave more reliable results. The peak potentials of the determined trace metals are shifted to more positive values compared to mercury drop or mercury coated electrodes, Zn displaying always 2 peaks, and Pb and Cd inversing their positions. For a deposition step of 120 s at –1.1 V, without stirring, the 25-µm gold-disk microelectrode has linear response for Cd, Cu, Hg, Mn, Pb and Zn from 0.2 µg L-1 (1 µg L-1 for Mn) to 20 µg L-1 (30 µg L-1 for Zn, Pb and 80 µg L-1 for Mn). In the same analytical conditions, the 125-µm gold-disk microelectrode shows linear behaviour for Cd, Cu, Pb and Zn from 1 µg L-1 (5 µg L-1 for Cd) to 100 µg L-1 (200 µg L-1 for Pb). When the sensitivities of the electrodes are divided by their surfaces, the 25-µm electrode is more sensitive than the 125-µm one. These microelectrodes have been validated for natural sample analysis by use in a quasi in-situ system to monitor Cu, Pb and Zn labile concentrations in the Deûle river (France), polluted by industrial activities.
Vis fullstendig beskrivelse
