Arsenic is ubiquitous in the earth’s crust in low concentrations. Elevated levels can be found in mineral deposits and ores. Arsenic from such deposits leaches into the groundwater in the form of arsenite (AsO33-) and arsenate (AsO43-), causing its contamination. In addition to the arsenic originating from natural sources, industry and agriculture contribute to the contamination to a lower extent. The guideline value for inorganic total arsenic in the World Health Organization’s «Guidelines for Drinking-water Quality» is set to 10 μg/L.

With a limit of detection (LOD) of 0.9 μg/L, anodic stripping voltammetry is a viable, less sophisticated alternative to atomic absorption spectroscopy (AAS) for the determination of arsenic. While AAS (and competing methods) can only be performed in a laboratory, anodic stripping voltammetry can be used conventionally in the laboratory or alternatively in the field using the 946 Portable VA Analyzer. The determination is carried out on the scTRACE Gold electrode.

Bottled mineral water

946 Portable VA Analyzer (scTRACE Gold version)
Figure 1. 946 Portable VA Analyzer (scTRACE Gold version)

The scTRACE Gold is electrochemically activated prior to the first determination. In the next step, the water sample and the supporting electrolyte are pipetted into the measuring vessel. The determination of arsenic is carried out with the 884 Professional VA or with the 946 Portable VA Analyzer using the parameters specified in Table 1. The concentration is determined by two additions of an arsenic standard addition solution.

Figure 2. 884 Professional VA fully automated for VA
Table 1. Parameters
Parameter Setting
Mode SQW – Square wave
Deposition potential -1 V
Deposition time 60 s
Start potential -0.3 V
End potential 0.4 V
Peak potential As 0V
  • scTRACE Gold

With a 60 s deposition time, this method is suitable for the determination of arsenic in water samples in concentrations from β(As(total)) = 0.9–10 μg/L.

Figure 3. Determination of arsenic in bottled mineral water (946 Portable VA Analyzer; 60 s deposition time)
Table 2. Results of the determination of As in mineral water
Sample As (μg/L)
Bottled mineral water 4.4
Author

Metrohm AG

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9100 Herisau

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