The synthesis and spectral characterization of a schiff base, 2-pyridinecarbaldehyde-p-phenylenedihydrazone (short for 2PC-PPH), were described. It was found that ferric ion (Fe3+) could selectively quench the fluorescence of 2PC-PPH, whereas many other metal ions, such as Mn2+, Zn2+, Cu2+, K+, Al3+, Ca2+, Ni2+, Co2+, Cr3+ and Fe2+, could not quench its fluorescence. Based on this, a sensitive method for ferric ion selective detection was established. Under the optimum conditions, the decreasing fluorescence intensity of 2PC-PPH is proportional to the concentration of Fe3+ within the range of 6.0 × 10−7–1.0 × 10−5 mol L−1. The detection limit (3σ) for Fe3+ determination is 3.6 × 10−7 mol L−1. The proposed method was successfully applied to determine iron in tea and milk powder.Graphical abstractHighlights► The interaction between Fe3+ and a schiff base was studied by spectroscopy. ► Ferric ion could selectively quench the fluorescence of it. ► A sensitive method for ferric ion selective detection was established.

•A fluorometric method for determination of EDTA is proposed.•The method bases on EDTA recover the fluorescence of a shiff base quenched by Fe3+.•The fluorescence recovery mechanism is formation of a ternary complex.•The method shows high specificity and high sensitivity for EDTA detection.A fast and sensitive fluorometric method for determination of an emerging pollutant, ethylenediaminetetraacetic acid (EDTA), was proposed based on the reversion of fluorescence quenching of 2-pyridinecarbaldehyde-p-phenyldihydrazone by ferric iron. It was found that Fe3+ could selectively quench the fluorescence of 2PC-PPH, while EDTA could recover it due to its strong coordination ability with Fe3+. Based on this, we established an “Off and On” fluorescence method for determination of EDTA. Under the optimum conditions, the linear range and detection limit (3S/N) for EDTA determination were 2.0 × 10−6 ∼ 1.4 × 10−5 mol L−1 and 1.5 × 10−7 mol L−1, respectively. The relative standard deviation for the determination of 7.0 × 10−6 mol L−1 EDTA was 3.7% (n = 11). The method was successfully applied to determination of EDTA in tap water, lake water and investigating degradation of EDTA by TiO2/UV process.A simple and sensitive “Off–On” fluorescence method have been developed for EDTA determination based on EDTA could recover the fluorescence quenching of 2-pyridinecarbaldehyde-p-phenyldihydrazone (2PC-PPH) by ferric iron.