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Presence of thallium in surface water is an indicator of industrial effluents and poses a serious health hazard if imbibed. Monitoring of thallium concentration can easily be done with anodic stripping voltammetry on the silver film modified scTRACE Gold.

This non-toxic method allows the determination of thallium concentrations between 10–250 µg/L. The determination is carried out with the 946 Portable VA Analyzer. The main advantage of this procedure is the unique design of the sensor, the scTRACE Gold electrode. It consists of a gold microwire working electrode, Ag/AgCl reference electrode, and a carbon auxiliary electrode on a ceramic substrate. The electrode is easy to handle and does not need extensive maintenance such as mechanical polishing. The possibility to re-plate the silver film allows a quick and easy regeneration of the sensor. This method is best suited for measurements in the field.

Drinking water, mineral water, sea water

946 Portable VA Analyzer
Figure 1. 946 Portable VA Analyzer

Prior to the first determination, the silver film is deposited from a silver solution on the scTRACE Gold electrode. In the next step, the electrodes are cleaned with ultrapure water and the measuring vessel is emptied. The water sample and the supporting electrolyte with EDTA are pipetted into the measuring vessel. The determination of thallium is carried out with a 946 Portable VA Analyzer using the parameters specified in Table 1. The concentration is determined by two additions of a thallium standard addition solution.

The scTRACE Gold is electrochemically activated prior to the first determination.

Table 1. Parameters
Parameter Setting
Mode SQW – Square wave
Deposition potential -1. 0 V
Deposition time 90 s
Start potential -1.0 V
End potential -0.25 V
Peak potential Tl -0.62 V
  • scTRACE Gold

The method is suitable for the determination of thallium concentrations up to 150 µg/L. The limit of detection with 90 s deposition time is approximately 10 µg/L.

Figure 2. Determination of thallium in tap water spiked with 30 µg/L
Table 2. Result
Sample Tl (µg/L)
Tap water spiked with 30 µg/L Tl 30.7
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Metrohm AG

Ionenstrasse
9100 Herisau

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Internal reference: AW VA CH4-0588-122019