Magnetic fluorine-functionalized covalent organic framework coupled with ambient mass spectrometry for rapid determination of benzoylurea insecticides in fruits and vegetables

Establishing a convenient and sensitive method for the enrichment and analysis of benzoylurea insecticides (BUs) in fruits and vegetables is essential for food safety monitoring. To this end, a novel fluorine-rich magnetic covalent organic framework (Fe₃O₄@COF-F) was designed and synthesized as an adsorbent in magnetic dispersion solid phase extraction (MDSPE), enabling efficient capture of BUs through synergistic interactions. This material exhibited rapid adsorption (4 min) and high adsorption capacities (150.1-163.1 mg g^-1). By coupling Fe₃O₄@COF-F-based MDSPE with pulsed direct current electrospray ionization (PDESI), an ambient mass spectrometry (AMS), a rapid approach was established for the determination of BUs in cucumbers, cabbages, and apples. The proposed MDSPE-PDESI-MS approach demonstrated good linearity (<i>r</i> > 0.995), low limits of detection (LODs) of 0.16-0.30 ng g^-1, and satisfactory spiked recoveries (80.56-93.98%). This method shows great potential for high-throughput and sensitive analysis of BUs in complex food matrices.