No health-based guideline value exists for zinc. However, to maintain good quality municipal drinking water, the United States Environmental Protection Agency (US-EPA) set a maximum concentration of 5 mg/L as the limit value. Typical concentrations in surface and ground waters are between 10–40 μg/L Zn. In tap water, this value can be up to 1 mg/L due to leaching of zinc from piping and fittings.
Anodic stripping voltammetry (ASV) on the ex-situ mercury film modified glassy carbon electrode provides a less complex alternative to atomic absorption spectroscopy (AAS) for zinc determination in drinking water. The main advantage of this method is the high sensitivity. With a deposition time of 10 s, the limit of detection for zinc is 0.15 μg/L. The linear working range goes up to approximately 300 μg/L. This method is suited for manual and automated systems.
Drinking water, mineral water, sea water
Prior to the first determination, the ex-situ mercury film is deposited on a freshly polished glassy carbon electrode. In the next step, the electrodes are cleaned with ultrapure water and the measuring vessel is emptied. Then the water sample and the supporting electrolyte are pipetted into the measuring vessel. The determination of zinc is carried out with the 884 Professional VA using the parameters specified in Table 1. The concentration is determined by two additions of a zinc standard addition solution.
|Mode||DP – Differential Pulse|
|Deposition potential||-1.4 V|
|Deposition time||10 s|
|Start potential||-1.2 V|
|End potential||-0.9 V|
|Peak potential Zn||-1.05 V|
- Working electrode: Glassy carbon (GC-RDE)
- Reference electrode: Ag/AgCl/KCl (3 mol/L)
- Auxiliary electrode: Glassy carbon rod
With the deposition time of 10 s, the method is suitable for samples between 10–150 μg/L zinc.