Determination of As(III) by anodic stripping voltammetry following double deposition and stripping steps at two gold working electrodes.

The double deposition and stripping steps were proposed to minimize interference and increase the sensitivity in anodic stripping voltammetry of As(III). Two working electrodes of drastically different surface areas were used for the measurements. Arsenic was first deposited at the gold film electrode of a large surface area. When the deposition step at this electrode finished, the electrode was moved at a short distance to the second electrode consisting of four gold microelectrodes. The arsenic stripped from the first electrode was partially deposited at the microelectrodes and the analytical signal was obtained by its oxidation. Due to double deposition of arsenic the interference of Cu(II) was minimized and the detection limit of As(III) was lowered by one order of magnitude. The calibration graph was linear from 5×10(-10) to 1×10(-8) mol L(-1) following deposition time of 300 s at the first and the second electrode.