Rapid screening detection of fluoroquinolone residues in milk based on turn-on fluorescence of terbium coordination polymer nanosheets

We report a facile, effective and rapid screening method for the determination of total fluoroquinolones(FQs) in milk using lanthanide coordination polymer nanomaterials as the sensing platform. The nonluminescent coordination polymer nanosheets(CPNSs) used in this work are composed of adenosine monophosphate(AMP) and terbium(Tb^(3+)) ions(AMP/Tb CPNSs). The as-prepared CPNSs were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy and fluorescence techniques. Tb^(3+) acts as the center ion of the coordination polymer, with AMP assembled through phosphate and amine groups. However, the reaction between FQs and AMP/Tb CPNSs noticeably turns on the fluorescence due to the strong coordination interaction between FQs and Tb^(3+). Under optimized conditions, the fluorescence intensity of AMP/Tb at 545 nm shows a linear relationship with FQ concentrations between 0.04 μmol/L and 5.0 μmol/L. The relative standard deviation(RSD) of the intraday precision is below 1%, and detection limits are as low as 0.01 μmol/L. The proposed method was successfully applied to the determination of FQs in milk samples.