Cadmium and lead in drinking water with screen-printed carbon electrodes

The provisional guideline values in the World Health Organization’s (WHO) «Guidelines for Drinking-water Quality» are set to 3 μg/L for cadmium and 10 μg/L for lead.

The anodic stripping voltammetry (ASV) technique performed on the ex-situ mercury film modified Metrohm DropSens screen-printed electrode (SPE) can be used to simultaneously detect concentrations as low as 0.3 μg/L for both elements. This is suitable to monitor the WHO guideline values.

The main advantage of this method lies in the innovative and cost-effective screen-printed electrode. It is a combined sensor consisting of a carbon working electrode, Ag/AgCl reference, and carbon auxiliary electrode on a ceramic substrate. The disposable sensor does not need maintenance such as mechanical polishing or mechanical cleaning. It can be used conventionally in the laboratory with the 884 Professional VA, or alternatively in the field with the 946 Portable VA Analyzer. This method is best suited for manual systems.

Drinking water, mineral water, sea water

Figure 1. 946 Portable VA Analyzer (SPE)

Prior to the first determination, the ex-situ mercury film is deposited in a separate step on the screenprinted electrode. 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 or with the 946 Portable VA Analyzer using the parameters specified in Table 1. The concentration of both elements is determined by two additions of a cadmium and lead standard addition solution.

Figure 2. 884 Professional VA, semiautomated system

**Table 1.** Parameters
Parameter	Setting
Mode	SQW – Square wave
Deposition potential	-1.3 V
Deposition time	60 s
Start potential	-1.0 V
End potential	-0.4 V
Peak potential Cd	-0.72 V
Peak potential Pb	-0.52 V

Screen-printed carbon electrode (Metrohm DropSens 11L)

With a 30 s deposition time, the limit of detection is around 1 μg/L, and the linear working range is up to 20 μg/L in the measuring solution for both elements.

Figure 3. Determination in mineral water spiked with 2 µg/L cadmium and lead

**Table 2.** Result
Sample	Cd (µg/L)	Pb (µg/L)
Mineral water spiked with 2 µg/L Cd and Pb	2.04	1.81

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Метром България ЕООД

12, Чипровци
1303 София

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Internal references: AW VA CH4-0593-042020; AW VA CH4-0594-042020