Chromogenic hydrazide Schiff base reagent: Spectrophotometric determination of CN- ion

A Schiff base reagent, Picolinohydrazide-naphthol (HL), is used for trace level detection of toxic CN- selectively in presence of eighteen other anions (SCN-, OCN-, S2O32-, HPO42-, H2PO4-, I-, ClO4-, HSO4-, SO42-, AsO43-, NO2-, AsO2- , Cl-, F-, HF2- , NO3- , Br-, N-3(-)) by visual color change, colorless to yellow, in DMSO/H2O (9:1, v/v) at pH, 72 (HEPES buffer) medium. The sensitivity of the probe shows that the limit of detection (LOD) is 7.08 mu M. The probable mechanism for the sensing behavior involves the deprotonation of naphthol-OH by CN- that has been authenticated by H-1 NMR titration and Mass spectra. The composition (1:1 mol ratio) is supported by Job's plot and binding constant (K-a, 1.5 x 10(4)M(-1)) is reported by Benesi-Hildebrand plot. Furthermore, a simple paper strip device is fabricated for the determination of CN- ion in water. DFT computation is carried out to explain the electronic spectral feature of the sensor. (C) 2019 Elsevier B.V. All rights reserved.