Electrochemical interference study of manganese and iron by multiplex method and the application for manganese analysis in drinking water

Graphical Abstract: We developed multiplex pattern recognition to determine Mn²⁺ in water systems using multiple electrodes and chronoamperometry. The proof-of-concept study illustrated how patterns could be generated and compared with a pattern library to help measure Mn²⁺ in the presence of Fe²⁺. The method can be further expanded to create sophisticated library for dealing with complicated sample matrix in the future.

Abstract

Manganese is an emerging concern in drinking water, due to its potential health and aesthetic effects. Although accurate and sensitive, spectroscopic techniques for Mn²⁺ detection are costly and not capable of rapid detection. Electrochemical methods, such as cathodic stripping voltammetry, have been intensively explored as portable low-cost methods for Mn²⁺ detection. Challenges of reliability and matrix interference are difficult to overcome with current electrochemical methods. Among the interference reagents, Fe²⁺ is one of the biggest challenges for Mn²⁺ detection. Herein, a new method based on multiplex chronoamperometry at potentials between 0.9 and 1.4 V by a multichannel potentiostat is explored for its ability for interference resistance and applicability for Mn²⁺ detection in real drinking water samples. Compared to conventional one-channel electrochemical techniques, the multiplex method generates a reliable pattern that is unique to the sample components. The interference between Mn²⁺ and Fe²⁺ is investigated and the results are promising even at 100:1 Fe²⁺:Mn²⁺ concentrations. The detection limit determined for the multiplex method was 25.3 μM, and the optimum recovery rate in a real drinking water sample was 99.8%.

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