Colorimetric chemosensor for Fe2+ and Fe3+ based on a ternary mixture of an anionic dye, a cationic polyelectrolyte, and a metal chelator in aqueous solution

A new colorimetric chemosensor based on a simple ternary mixture of an anionic dye, pyrogallol red (PR), a cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDADMAC), and a metal chelator, N-(2-hydroxyethyl) ethylenediaminetriacetic acid (HEDTA) for the colorimetric detection of Fe2+ and Fe3+ has been developed in an aqueous solution buffered at pH 5. Upon addition of Fe2+ or Fe3+ to the mixture, the absorption spectra showed a bathochromic shift; correspondingly, the solution color changed from red to blue, whereas other metal ions basically resulted in insignificant spectral and color changes. From the competitive experiments, no obvious interferences for the colorimetric detection of Fe2+ and Fe3+ were observed in the presence other metal ions. The results indicated that the mixture could be used as a potential Fe2+ and Fe3+ colorimetric and naked eye chemosensor in aqueous media. This research demonstrates that the ternary ensemble consisted of an organic dye, an oppositely charged polyelectrolyte, and a metal chelator is a versatile and convenient tool for the facile preparation of a novel chemosensor system.