A water-soluble fluorescent fluoride ion probe based on Alizarin Red S-Al(III) complex

A new water-soluble fluorescent fluoride ion signaling system has been developed based on the ligand exchange mechanism in aqueous medium. This procedure is based on the exchange of two Alizarin Red S (ARS) molecules coordinated to AI(Ill) by fluoride ion without interference from other common anions. The binary complex of ARS with AI(Ill) provides a sensitive signaling system for fluoride ion in the concentration range from 5 x 10(-6) to 3 x 10(-4) M. The ligand exchange reaction of ARS-AI(III) complex with fluoride ion has been investigated by UV-vis and fluorescence spectroscopies combined with the AM I semi-empirical quantum chemical calculations. The pale orange fluorescence 575 nm) exhibited by the complex upon excitation at 435 nm decreases in intensity with fluoride addition with a detection limit of 0.1 mg L-1. (D 2006 Elsevier B.V. All rights reserved.