Fe-MOF-based fluorescent sensor with on/off capabilities for the highly sensitive detection of tert-butylhydroquinone in edible oils

In this work, a "turn off-on" fluorescent sensor was developed for highly sensitive determination of tert-butylhydroquinone (TBHQ) based on an Fe(III)-based metal-organic framework (Fe-MOF). An Fe-MOF with an octahedral structure was synthesized via a simple hydrothermal method using ferric chloride hexahydrate and 2-aminoterephthalic acid (NH2-BDC) as raw materials. The fluorescence of Fe-MOF is extremely weak owing to ligand-to-metal charge transfer (LMCT) and internal filtration effect (IFE). When the system contained TBHQ, the binding of TBHQ to Fe(III) inhibited the LMCT of the fluorescent ligand NH2-BDC to Fe(III), releasing the fluorescence of NH2-BDC and thus restoring the fluorescence. With this as the basis, a rapid, sensitive, and selective fluorescence sensor is developed for the detection of TBHQ. Under the optimal conditions, TBHQ showed good linearity with fluorescence intensity in the range of 0–1.5 × 102 μmol L−1 and a detection limit of 0.0030 μmol L−1 (S/N = 3). The selectivity, reproducibility, and stability of the developed Fe-MOF-based sensors are comprehensively studied. Finally, the practicality of the method is verified by examining the detection of TBHQ in soybean oil; the results are consistent with those obtained using conventional high-performance liquid chromatography.