Bi-component sensing platform for the detection of Cd(2+), Fe(2+)and Fe(3+) ions.

The ability of N-(1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)isonicotinamide (naphydrazide) or 2,6-pyridinedicarboxylic acid (2,6-H(2)pdc) individually or as a bi-component system in distinguishing and detecting Fe(3+) or Fe(2+) and Cd(2+) 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-H(2)pdc for assessing the interactions with ferrous and ferric ions showed characteristic distinctions. The detection limit for Fe(3+) analysed through UV-visible spectroscopy using naphydrazide was 0.46 μM, whereas it was 1.28 μM using 2,6-H(2)pdc. Naphydrazide together with Fe(3+) allowed distinguishing Cd(2+) ions from Zn(2+) and Fe(2+) ions. The bi-component system was useful for the selective detection of Cd(2+) ions using fluorescence spectroscopy, with a detection limit for Cd(2+) ions of 18.31 μM. The presence of Fe(2+) and Cd(2+) ions in a solution of the bi-component had resulted white-light emission. An analogous compound N,N'-(1,3,6,8-tetraoxobenzo[lmn][3,8]phenanthroline-2,7(1H,3H,6H,8H)-diyl)diisonicotinamide (binaphydrazide) was found unsuitable for such detections. Two 2,6-pyridinedicarboxylate Fe(3+) 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(3+) or Fe(2+) from Cd(2+) ions.