Bi-component sensing platform for the detection of Cd, Feand Fe ions.

The ability of -(1,3-dioxo-1-benzo[de]isoquinolin-2(3)-yl)isonicotinamide (naphydrazide) or 2,6-pyridinedicarboxylic acid (2,6-Hpdc) individually or as a bi-component system in distinguishing and detecting Fe or Fe and Cd ions was investigated. The use of these molecules as single or bi-component analytes in absorption or emission spectroscopy studies showed that under specific conditions each had their own merits for specific purposes. UV-visible spectroscopic studies of 2,6-Hpdc for assessing the interactions with ferrous and ferric ions showed characteristic distinctions. The detection limit for Fe analysed through UV-visible spectroscopy using naphydrazide was 0.46 μM, whereas it was 1.28 μM using 2,6-Hpdc. Naphydrazide together with Fe allowed distinguishing Cd ions from Zn and Fe ions. The bi-component system was useful for the selective detection of Cd ions using fluorescence spectroscopy, with a detection limit for Cd ions of 18.31 μM. The presence of Fe and Cd ions in a solution of the bi-component had resulted white-light emission. An analogous compound ,'-(1,3,6,8-tetraoxobenzo[lmn][3,8]phenanthroline-2,7(1,3,6,8)-diyl)diisonicotinamide (binaphydrazide) was found unsuitable for such detections. Two 2,6-pyridinedicarboxylate Fe complexes possessing protonated naphydrazide or binaphydrazide were prepared and characterised. These complexes were also found unsuitable for the detection of the said ions in solution. Electrochemical studies with the bi-component system showed that cyclic voltammograms could distinguish Fe or Fe from Cd ions.