Flow electrochemical analyses of zinc by stripping voltammetry on graphite felt electrode

A flow sensor for trace analysis of zinc, using graphite felt as working electrode is reported here. A flow cell, well-adapted to 3-D porous electrodes and capable to do both the preconcentration step at a cathodic potential and the stripping of the zinc was successfully developed. It was demonstrated that this cell allows to obtain better electrochemical signals for Zn2+ compared to a standard three-electrodes cell and that the percolation during accumulation increases the kinetics of electrodeposition. The influence on Zn2+ signal of the deposition potential, the time of deposition and the flow rate was studied. The resulting sensor shows a linear response towards Zn2+ with a linear range of 10−6–10−4 M and a limit of detection of 5×10−7 M for an analysis time of 5 min. The interferences study showed that the Cr3+, Pb2+, Cd2+ ions have a small effect on the Zn electrochemical signal, whereas Fe3+, Cu2+, Co2+ and Ni2+ ions strongly influence it. The electrode was tested on real samples (tap water spiked with Zn2+, food supplement) with a good recovery by applying the standard addition method.