A functionalized magnetic covalent organic framework for sensitive determination of trace neonicotinoid residues in vegetable samples

A functionalized magnetic covalent organic framework containing the nitro groups (Fe3O4@COF-(NO2)(2)) with core-shell structure was synthesized for magnetic solid phase extraction (MSPE) of six neonicotinoid insecticides residue in vegetable samples. The structure of Fe3O4@COF-(NO2)(2) was investigated by various characterization techniques. The Fe3O4@COF-(NO2)(2) exhibits the excellent thermal and chemical stability, high surface area (254.72 m(2) g(-1)), total pore volume (0.19 cm(3) g(-1)), high magnetic responsivity (27.7 emu g(-1)), which can be used as an ideal adsorbent for rapid isolation and enrichment of target analytes. A sensitive method was developed by using Fe3O4@COF-(NO2)(2)-based MSPE coupled with HPLC with UV detection. It offered good linearity within the range of 0.1-30 ng mL(-1), low limits of detection (S/N = 3) of 0.02-0.05 ng mL(-1). Furthermore, high enrichment factors of 170-250 for six neonicotinoid insecticides were obtained. The applicability of Fe3O4@COF-(NO2)(2) is demonstrated for measuring trace neonicotinoid residues in vegetable samples with satisfactory recoveries, which ranged from 77.5 to 110.2%. The results indicated that the Fe3O4@COF-(NO2)(2) microspheres offer great potential for efficient extraction of neonicotinoid insecticides from complex samples. (C) 2020 Elsevier B.V. All rights reserved.