A new colorimetric chemosensors for Cu2+ and Cd2+ ions detection: Application in environmental water samples and analytical method validation

•Detection of Cu2+ and Cd2+ ions has gained significance by virtue of its key role in biological and environmental science.•The R3 and R4 showed instantaneous color change from colorless to yellow in the presence of Cu2+ and Cd2+ ions respectively.•The proposed detection methods were validated and successfully applied to the different environmental water samples.•R3 and R4 showed high selectivity of towards Cu2+ and Cd2+ ions in the presence of other tested cations and anions.•Detection limit of 2.8 μM for Cu2+ ions and 0.20 μM for Cd2+ ions with good linear range is obtained for R3 and R4.

A new heterocyclic thiophene-2-caboxylic acid hydrazide based chemosensor R1 to R4 were designed, synthesized and characterized by various spectroscopic techniques like FT-IR, UV-Vis, 1H NMR, 13C NMR, Mass and SC-XRD. The chemosensor R3 showed a significant color change from colorless to yellow in the presence of Cu2+ ions and chemosensor R4 showed a significant color change from colorless to yellow in the presence of Cd2+ ions over the other tested cations such as Cr3+, Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Zn2+, Ag2+, Al3+, Pb2+, Hg2+, K+, Ca2+ and Mg2+. The high selective and sensitivity of R3 towards Cu2+ and R4 towards Cd2+ ions was confirmed by UV-Vis spectroscopic study. The R3 showed a red shift in the presence of Cu2+ ions by Δλmax 67 nm and R4 showed a red shift in the presence of Cd2+ ions by Δλmax 105 nm in the absorption spectrum. The binding stoichiometric ratio of the complex between R3 - Cu2+ and R4 - Cd2+ ions have been found to be 1:1 using the B-H plot. Under optimized experimental conditions, the R3 and R4 exhibits a dynamic linear absorption response range, from 0 to 50 μM for Cu2+ ions and 0 to 30 μM for Cd2+ ions, with the detection limit of 2.8 × 10−6 M for Cu2+ and 2.0 × 10−7 M for Cd2+ ions. The proposed analytical method for the quantitative determination of Cu2+ and Cd2+ ions was validated and successfully applied for the environmental samples with good precision and accuracy.

Graphical abstractDownload high-res image (307KB)Download full-size image