A highly selective colorimetric sensing of CN– ion by a hydrazine appended Schiff base and its application in detection of CN– ion present in tobacco and food samples

Abstract

• Colorimetric sensing – Fast response – Economic senor. • Hydrazone based colorimetric Schiff base HL-1 have been prepared towards CN – ions recognition with naked eye. • Bathochromic shift produced with significant color change. • The recognition mechanism based on deprotonation and interaction confirmed with NMR, FT-IR, ESI-MS spectroscopic techniques. • The practical application of HL-1 was carried out in tobacco and food samples (kidney bean, apple seed, cassava, flax seeds, almond skin, plum seeds). A simple, cost-effective, and highly selective colorimetric chemosensor, was designed and synthesized from 2,4-dinitrophenyl hydrazine and ethyl acetoacetate. The formation of the HL-1 ethyl-( E )-3-(2-(2,4-dinitrophenyl)hydrazono)butanoate was confirmed by spectral techniques. The receptor HL-1 was found to show a colorimetric response of the colour change from yellow to brown towards CN – ion, due to de-protonation and intra-ligand charge transfer. The receptor HL-1 interacts with cyanide in a 1:1 stoichiometric manner with a detection limit of 7.39 × 10 −7 M. Receptor HL-1 could be recyclable by treatment with TFA. The sensing behaviour of the receptor was further enunciated by computational studies and it’s also be efficiently used to detect trace amounts of cyanide present in food samples such as cassava peel, apple seeds, kidney beans, tobacco, flax seeds, almond skin, and plum seeds. Moreover, HL-1 would be used for practical applications like visible colorimetric test kits such as cotton swabs, and test paper strips.