A Fluorescein-based Fluorogenic Probe for Fluoride Ion Based on the Fluoride-induced Cleavage of tert-butyldimethylsilyl Ether

A highly sensitive and selective fluorogenic probe for fluoride ion, fluorescein di-tert-butyldimethylsilyl ether (FTBS), was designed and synthesized. FTBS was a colorless, non-fluorescent compound and was synthesized via the one-step reaction of fluorescein with tert-butyldimethylsilyl chloride. Upon incubation with fluoride ion in DMF-water solution (7 : 3, V/V), the Si-O bond of FTBS was cleaved, causing a large increase in fluorescence intensity and thereby allowing a selective detection of fluoride ion. The fluorescence increase is linearly with fluoride concentration in the range 0.1–2.0 μmol L−1 with a detection limit of 0.041 μmol L−1 (3σ). The excellent selective signaling behavior of the proposed probe was found to originate from the high affinity of silicon toward fluoride ion. The method has been successfully applied to the fluoride determination in multi-trace elements injection and toothpaste samples, and the results are agreed well with those obtained by the fluoride-ion selective electrode method.