Fluorescent siderophore-based chemosensors: iron(III) quantitative determinations

A highly sensitive and selective method is described for a rapid and easy d etermination of iron(III). This procedure is based on fluorimetric detectio n combined with the attractive properties of siderophores and biomimetic li gands, which are strong and selective ferric chelators, Azotobactin delta, a bacterial fluorescent siderophore, three fluorescent derivatives of desfe rriferrioxamine B with a linear structure (NBD-, MA-, NCP-desferriferrioxam ine B) and one tripodal biomimetic ligand of desferriferrichrome carrying a n anthracenyl fluorescent probe were examined. A very efficient static quen ching mechanism by iron was observed for all the ligands considered in this work. Our results identify azotobactin delta as the most promising chemose nsor of ferric traces in water, more sensitive than the NBD-desferriferriox amine B fluorescent ligand. Under more lipophilic conditions, the anthryl-d esferriferrichrome biomimetic analogue showed similar analytical potential and was found to be more sensitive than the lipophilic MA- and NCP-desferri ferrioxamine B. Their detection limits were respectively 0.5 ng mL(-1) for azotobactin delta and 0.6 ng mL(-1) for the anthryl tripodal chelator. The calibration curves were linear over the range 0-95 ng mL(-1) and 0-180 ng m L(-1). Various foreign cations have been examined and only copper(II) and a luminium(III) were shown to interfere when present in similar concentration s as iron(III). The developed procedure using fluorescent siderophores or b iomimetic ligands of iron(III) may be applied (1) to monitor iron(III)-depe ndent biological systems and (2) to determine iron(III) quantitatively in n atural waters and in biological systems.