Detection of Pyrethroids in Food by Immunofluorescence Enhanced Method Based on Three-Layer Core-Shell Structure Upconversion Materials.

A novel rare earth upconversion nanomaterial with a three-layer sandwich core-shell structure was synthesized by an improved thermal decomposition method, and the morphology, fluorescence intensity and diffraction peak position of the new material were characterized by TEM (transmission electron microscope), XRD (Powder X-ray diffraction)and fluorescence spectrophotometer. The inert core/active shell/inert shell design improved the upconversion luminous efficiency of the new material several times. FTIR (Fourier transform infrared spectroscopy)characterization showed that the surface of activated upconversion nanoparticles was modified with silicon shell and amino group. Combined with the characteristics that aminoated polystyrene magnetic microspheres could be separated by the magnetic field, an upconversion magnetic separation immunoassay method for the detection of pyrethroid pesticide residues was established. The capture probe competed with the pyrethroid standard, combined the signal probe, and measured the fluorescence signal value formed by the capture probe signal probe complex at 542 nm under 980 nm excitation light. The LOD (limit of detection)of fenpropathrin was 0.01 μg/L, cypermethrin was 0.015 μg/L, and fenvalerate was 0.011 μg/L. Through the actual sample detection of apple, cabbage and other samples, the recovery rate of pyrethroids was between 83.4~97.8%. The comparison with the HPLC (high performance liquid chromatography)detection results showed that the established method had good accuracy, and could realize the quantitative analysis of pyrethroids in food.