Synthesis of a magnetic covalent organic framework for the extraction and detection of benzimidazole residues in food matrices by UPLC-MS/MS.

A novel magnetic covalent organic framework was innovatively developed as a high-performance adsorbent for magnetic solid-phase extraction (MSPE) of benzimidazole veterinary drug residues in food matrices. The synthesized nanocomposite features a well-ordered core-shell architecture with a notable specific surface area and remarkable superparamagnetic behavior, facilitating rapid phase separation within 3 min under a magnetic field. Seven representative benzimidazoles (albendazole sulfoxide, fenbendazole sulfoxide, flubendazole, fenbendazole, cambendazole, cyclobendazole, albendazole sulfone) were selected to systematically evaluate the extraction efficiency and method performance. The material exhibited superior adsorption capacities (46.2–62.0 mg/g) through synergistic π-π conjugation, hydrogen-bonding, and hydrophobic interactions with benzimidazole moieties. Notably, the adsorbent maintained 90% of its initial capacity after six regeneration cycles, demonstrating excellent reusability. An innovative MSPE-UPLC-MS/MS methodology was established for detecting trace-level residual compounds in food matrices (milk and honey), with determination coefficient R² ≥ 0.991. The method achieved unprecedented sensitivity with detection limits of 0.015–0.131 µg/kg and quantification limits of 0.050–0.436 µg/kg. Validation studies showed satisfactory recoveries (83.67-102.96%) and good precision (RSD < 8.63%) across four spiking levels.