Extraction of benzoylurea insecticides from tea leaves based on thermoplastic polyethyleneimine embedded magnetic nanoparticle carbon materials.

A novel mosaic structured core-shell composite, Silica@C/Ni (Sil@C/Ni), has been prepared by embedding Ni nanoparticles on the surface of silica microspheres via coordination and carbonization reduction, and was used as magnetic solid-phase extraction sorbents in combination with high performance liquid chromatography (HPLC) for the extraction and determination of four benzoylurea insecticides (BUs) in tea leaves. Based on the fact that hydrogen bonding and hydrophobic interactions exist between the material and BUs, allowing BUs on the surface of the material can achieve rapid mass transfer and improved sorption performance, satisfactory extraction recoveries have been achieved in practical sample applications. Under the optimized experimental conditions, the linear ranges were 0.5-200 µg L for diflubenzuron and triflumuron, 1.0-200 µg L for teflubenzuron and 0.8-200 µg L for flufenoxuron with the correlation coefficients R ≥ 0.9991. The method has limits of detection and limits of quantification of 0.2-0.4 µg L and 0.5-1.0 µg L, respectively. The intra-day and inter-day relative standard deviations were less than 5%. The actual sample recoveries were 76.63-95.26%. In addition, Sil@C/Ni was used repeatedly for 15 times and still showed a relatively satisfactory recovery of the four BUs. Therefore, Sil@C/Ni has a high stability and can be used as an ideal magnetic solid phase extraction sorbent for the trace enrichment of BUs in tea-leaf samples.