A highly selective quinoline-appended Schiff base for colorimetric recognition of arsenite in the presence of cyanide: A masking approach with real-life applications

A novel quinoline-based chemosensor, TRP-5 , was designed and synthesized from 2-morpholinoquinoline-3-carbaldehyde and 2,4-dinitrophenyl hydrazine, and characterized by various spectroscopic techniques. The sensor displayed high selectivity and sensitivity towards AsO 2 − ions in presence of interfering CN − ions, with a colorimetric response from yellow to pink. The receptor TRP-5 interacts with AsO 2 − and CN − in a 1:1 stoichiometric manner with a lower detection limit of 5.63 × 10 −8 M and 8.5 × 10 −7 M, respectively and could be recyclable using 1 N HCL. TRP-5 interacted with both analytes through a binding mechanism involving deprotonation followed by intra-ligand charge transfer, as confirmed by 1 H NMR, FTIR, and DFT analysis. To prevent cyanide interference, hydrogen peroxide was used as an effective masking agent, which enabled selective AsO 2 − detection. The sensor was stable across pH 6–12 and could be used for on-site recognition for AsO 2 − ions with visible colorimetric test kits such as test paper strips. The receptor was also used for sensing arsenite ions in environmental water samples and produced high recoveries.