A colorimetric chemosensor for quantification of exchangeable Cu2+ in soil

Chemosensors have already demonstrated potential for the detection and imaging of metal ions in solutions and biological systems, however, their applications to soil analysis are limited. This study explores the potential of utilizing a chemosensor for the detection of exchangeable Cu2+ in soils via qualitative (solution visual color change) and quantitative (UV–Vis spectrophotometry) approaches. Montmorillonite and kaolin clays were doped with Cu(NO3)2 solutions from 2.5 to 50 mM, and contaminated soil samples were collected from a historic copper mine. The exchangeable Cu2+ was extracted using a standard CaCl2 cation exchange approach, and the Cu2+ concentration in the resulting solutions determined by UV–Vis spectrophotometry, using a chemosensor, and compared to traditional ICP-MS analysis. Analytical results showed that the chemosensor provided a visual response in contaminated soils at concentrations of 25 μM and quantitative detection to concentrations of 1 μM using UV–Vis spectrophotometry. This work demonstrates the first reported chemosensor for exchangeable Cu2+ with application to soil systems. For Table of Contents Only. [Display omitted] •A novel method for the detection of exchangeable Cu2+ on soils has been developed.•Exchangeable Cu2+ determination using chemosensor is as accurate as ICP-MS.•The chemosensor method allows for portable detection of Cu2+ on soils.