A ferrocene-based probe for colourimetric/electrochemical detection of bisulfite ions and its practical application

A simple ferrocene-based organic probe (AK5) is described for selective and sensitive colourimetric/electrochemical detection of HSO3- ions in a 95 % aqueous solution. Upon adding HSO3− ions, the colour of the solution changes from brown to colourless instantaneously. The plausible mechanism of detection of HSO3− ions by AK5 was illustrated by 1H NMR, 13C NMR, HR-MS and DFT/TD-DFT analysis, which revealed nucleophilic addition of HSO3− ion to olefinic C-atom. The limits of detection (LOD) are determined to be 5.58 and 0.12 µM in colourimetric and electrochemical methods, respectively. The probe is successfully applied to estimate the levels of HSO3− ions in natural water and red wine samples.