Abstract: In this study, a novel covalent organic framework material, Fe3O4@COF(OT-BDD), was synthesized using 2,3-dihydroxyterephthalaldehyde (BDD) and o-tolidine (OT). This material was applied in magnetic solid phase extraction (MSPE) coupled with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) for the efficient determination of four types of aflatoxins (AFs) in nut samples. The experimental results showed that the developed analytical method exhibited excellent linearity over the concentration range from 0.1 to 100 μg/kg, with determination coefficients (R2) exceeding 0.999. Recovery rates for spiked sample ranged from 86.1% to 104.2%, and intra- and inter-day precisions, expressed as relative standard deviations (RSDs), were less than 11.2%. The limits of detection (LODs) ranged from 0.05 to 0.12 μg/kg, and the limits of quantification (LOQs) ranged from 0.13 to 0.37 μg/kg. The COF material synthesized in this study exhibited strong adsorption capacity for Afs and enabled rapid, accurate, and sensitive detection of AFs in nut samples, effectively addressing the limitations of traditional methods in handling the complex matrix of nut-based food products.

Key words: covalent organic frameworks; aflatoxins; magnetic solid phase extraction; nuts