A new colorimetric chemosensors for Cu and Cd ions detection: Application in environmental water samples and analytical method validation.

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, H NMR, C NMR, Mass and SC-XRD. The chemosensor R3 showed a significant color change from colorless to yellow in the presence of Cu ions and chemosensor R4 showed a significant color change from colorless to yellow in the presence of Cd ions over the other tested cations such as Cr, Mn, Fe, Fe, Co, Ni, Zn, Ag, Al, Pb, Hg, K, Ca and Mg. The high selective and sensitivity of R3 towards Cu and R4 towards Cd ions was confirmed by UV-Vis spectroscopic study. The R3 showed a red shift in the presence of Cu ions by Δλ 67 nm and R4 showed a red shift in the presence of Cd ions by Δλ 105 nm in the absorption spectrum. The binding stoichiometric ratio of the complex between R3 - Cu and R4 - Cd 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 Cu ions and 0 to 30 μM for Cd ions, with the detection limit of 2.8 × 10 M for Cu and 2.0 × 10 M for Cd ions. The proposed analytical method for the quantitative determination of Cu and Cd ions was validated and successfully applied for the environmental samples with good precision and accuracy.