An inner filter effect based Schiff base chemosensor for recognition of Cr(VI) and ascorbic acid in water matrices

An effective and simple fluorescent sensing approach for recognition of Cr(VI) using a Schiff base chemosensor, N'-[(E)-(3,4-dimethoxyphenyl) methylidene]furan-2-carbohydrazide, was developed. Fluorescence of the chemosensor was adequately quenched by Cr(VI) through primary and secondary inner filter effects. The linear recognition range of Cr(VI) was from 1 mu M to 500 mM with a detection limit of 0.175 mu M. The switched off fluorescence of the chemosensor-Cr(VI) solution was effectively switched on with the addition of L-ascorbic acid in the concentration range of 10 mu M to 390 mu M with a LOD of 2.46 mu M. The mechanism proposed for fluorescence turn-on of quenched fluorescence of the Cr(VI)-chemosensor solution of ascorbic acid is the reduction of Cr(VI) to Cr(III) by L-ascorbic acid which resulted in the elimination of both primary and secondary inner filter effects and the recovery of fluorescence of the chemosensor. The method presented in this paper was found to be effective in recognition of Cr(VI) in tap water and groundwater and ascorbic acid in human serum and vitamin C tablets.