Two new manganese-based phosphomolybdate compounds as electrochemical sensors for the highly sensitive trace determination of heavy metal Cr(vi) ions

Abstract

A convenient and sensitive method for the determination of heavy metal Cr(VI) ions is developed. Here, two reductive polyoxometalate-based compounds, Mn₂{Mn[Mo₆O₁₂(OH)₃(H₂PO₄)(PO₄)₃]₂}[H₂(X-AP)]₄ [X = 3 (1) or 4 (2), AP = aminomethylpyridine], were prepared by a hydrothermal method and used as electrochemical sensors for the detection of Cr(VI). Compound 1 is a two-dimensional (2D) layer, while compound 2 is a three-dimensional (3D) supramolecular framework connected by hydrogen-bond interactions. The electrochemical detection of Cr(VI) on carbon paste electrodes modified by compounds 1 and 2 (1-CPE and 2-CPE) is studied. The limits of detection (LODs) for compounds 1 and 2 were 0.48 μM and 0.0916 μM, respectively, and met the standard of Cr(VI) in drinking water set by World Health Organization (WHO) (less than 0.962 μM). Importantly, they exhibited good selectivity to Cr(VI) ions in the presence of various metal ions, which proved their strong anti-interference abilities. This work is a continuation of {P₄Mo₆}-based compounds as electrocatalysts and exhibits great significance for environmental monitoring and protection.