Colorimetric Chemosensor Based on Fe₃O₄ Magnetic Molecularly Imprinted Nanoparticles for Highly Selective and...

Long-term use of norfloxacin (NOR) will cause NOR residues in foods and harm human bodies. The determination of NOR residues is important for guaranteeing food safety. In this study, a simple, selective, and label-free colorimetric chemosensor for in situ NOR detection was developed based on Fe₃O₄ magnetic molecularly imprinted nanoparticles (Fe₃O₄ MMIP NPs). The Fe₃O₄ MMIP NPs showed good peroxidase-like catalytic activity to 3,3',5,5'-tetramethylbenzidine (TMB) and selective adsorption ability to NOR. The colorimetric chemosensor was constructed based on the Fe₃O₄ MMIP NPs-H₂O₂-TMB reaction system. The absorbance differences were proportional to the concentrations of NOR in the range of 10-300 ng/mL with a limit of detection at 9 ng/mL. The colorimetric chemosensor was successfully applied to detect NOR residue in milk. The recovery range was 78.2-95.81%, with a relative standard deviation of 2.1-9.88%. Together, the proposed colorimetric chemosensor provides a reliable strategy for the detection of NOR residues in foods.