Lead contamination of drinking water is a concern to all living in old cities where lead pipes and soldering are still present. Electrochemical methods are simple, inexpensive, and thus are promising for analysis of this type of contamination. However, a major inconvenience with the detection of metal ions is the need to acidify the solution. Otherwise, the measurements are usually misrepresentative because of hydrolysis and metal hydroxide precipitation. Presence of anions like CO32- and PO43- in tap water also leads to Pb precipitation. Membrane electrolysis with an anion-exchange membrane can be used to substitute the need for adding acid to the sample. The protons needed to acidify the solution are generated as a result of electrochemical water oxidation. This allows for the precise control of the pH and conductivity and replaces classic reagent sample preparation. In such a setup, the cathode and anode are separated by the anion-exchange membrane to prevent proton oxidation at the anode. Applying +4.5 V to the electrolytic cell for 30 min would result in a rapid increase in acidity in the anodic compartment (pH 2), which is sufficient to transform most of Pb species in the soluble format. At the same time, due to the anomalously high mobility of protons, the conductivity of solution would significantly increase. Pb was detected using anodic stripping square wave voltammetry. The calibration graph for Pb quantification in acidified tap water was linear in the range of 24.0 – 400 nM (5 – 83 µg L-1) that includes the target values of 48 nM (10 µg L-1) and 72 nM (15 µg L-1) suggested by the World Health Organization and the Environmental Protection Agency respectively. To automize Pb detection and transform the membrane electrolysis cell into an automated device, the configuration for Pb voltammetric analysis was integrated into the membrane electrolysis setup.

Membrane electrolysis for reagent-free sample preparation of tap water for voltammetric Pb detection

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