To reduce the toxic effects of cadmium on the kidneys, skeleton, and the respiratory system, as well as the neurotoxic effects of lead, the provisional guideline values in the World Health Organization’s (WHO) «Guidelines for Drinking-water Quality» are set to a maximum concentration of 3 µg/L for cadmium and 10 µg/L for lead.
The powerful anodic stripping voltammetry (ASV) technique on the ex-situ mercury film modified glassy carbon electrode is more than sufficient to monitor the proposed WHO guidelines for Cd and Pb in drinking water. The main advantage lies in the ultrahigh sensitivity of this method. With a deposition time of 30 s, a limit of detection for β(Cd) = 0.02 μg/L and β(Pb) = 0.05 μg/L can be reached. The linear range for both elements goes up to approximately 50 μg/L using the same deposition time. The ability to re-plate the mercury film allows a quick and easy regeneration of the sensor. This method is best suited for both manual and automated systems, allowing the determination in a sample series comprised of a low to medium number of samples.
Drinking water, mineral water, sea water
Prior to the first determination, the ex-situ mercury film is deposited on the 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 simultaneous determination of cadmium and lead is carried out with the 884 Professional VA using the parameters specified in Table 1. The concentration of both elements is determined by two additions of a cadmium, lead standard addition solution.
| Parameter | Setting |
|---|---|
| Mode | DP – Differential Pulse |
| Deposition potential | -1.0 V |
| Deposition time | 90 s |
| Start potential | -0.85 V |
| End potential | -0.25 V |
| Peak potential Cd | -0.65 V |
| Peak potential Pb | -0.48 V |
- Working electrode: Glassy carbon (GC-RDE)
- Reference electrode: Ag/AgCl/KCl (3 mol/L)
- Auxiliary electrode: Glassy carbon rod
The method is suitable for the determination of cadmium and lead in concentrations up to 25 µg/L. The limit of detection for 30 s deposition time is approximately 0.02 µg/L for cadmium and 0.05 µg/L for lead.
| Sample | Cd (µg/L) | Pb (µg/L) |
|---|---|---|
| Tap water | 0.02 | 1.76 |
Application Bulletin 241: Determination of cadmium and lead by anodic stripping voltammetry at a mercury film electrode
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