A new colorimetric chemosensors for Cu2+ and Cd2+ 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-1 NMR, C-13 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 Delta lambda(max) 67 nm and R4 showed a red shift in the presence of Cd2+ ions by Delta lambda(max) 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 mM for Cu2_ ions and 0 to 30 mM for Cd2+ ions, with the detection limit of 2.8 x 10(-6) M for Cu2+ and 2.0 x 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. (C) 2017 Elsevier B.V. All rights reserved.