Development of a fluorescent strategy for quantification of fluoride ions in foods and toothpaste

Fluoride is one of the key chemical elements in human life and chemical industry, which also shows the high toxicity. A fluorescent probe (ZYP-1) based 1,8-naphthalimide has been prepared for fluoride ions detection, and exhibited high selectivity and sensitivity towards real samples. F-19 NMR and H-1 NMR titration was further determined the interaction between analyte and ZYP-1, and show the strong Lewis acidic boron atom of probe can complex basic fluoride. Theoretical calculations demonstrate that the coordination process will inhibit the photoinduced electron transfer (PET) from fluorophore to boron center that results in the increased fluorescence intensity at 540 nm. The limit of detection (LOD) of ZYP-1 for F- was found as low as 33 nM in acetonitrile. The probe can successfully applied in various liquid and solid samples of foods (fish fillets, tea leaves, water, and milk) and toothpaste to detect fluoride, which render broad application prospect.