Stripping voltammetry at preplated mercury coated microelectrodes in flowing solutions

A flow system is described in which stable preplated mercury coatings on microelectrodes can be obtained due to minimised handling of the electrode and the fact that potentiostatic control can be maintained also between the experiments. Compared to the deposition of mercury and subsequent transfer of microelectrodes, the use of the flow system gives better control of the mercury deposition step and also reduces the risk of losing the coating during solution exchange. It is shown that copper determinations can be made in low ionic strength media (3 x 10(-7) M HNO3) using mercury coated carbon fibre microelectrodes and anodic stripping voltammetry. The flow system has also been used for adsorptive stripping voltammetric determinations of 10(-9) M concentrations of nickel at gold amalgam microelectrodes. The reproducibility in the measurements with the mercury coated carbon fibre electrodes was found to depend on the reproducibility in the electrode heat sealing process.