Synthesis of a magnetic covalent organic framework as sorbents for solid-phase extraction of aflatoxins in food prior to quantification by liquid chromatography-mass spectrometry

A novel magnetic dispersive SPE (MDSPE) based on magnetic covalent organic framework (M-COF) coupled with liquid chromatography-mass spectrometry (LC-MS/MS) was developed for the determination of AFB1, AFB2, AFG1 and AFG2 in food matrices (milk, edible oil and rice). The M-COF was designed and constructed by using two novel monomers of 1,2,4,5-Tetrakis-(4-formylphenyl)benzene (TFPB) and p-Phenylenediamine (PPD) at room temperature. Various techniques were used to verify the successful synthesis of the M-COF. The adsorption capacities of M-COF for AFs were in the range of 69.5-92.2 mg/g. Major parameters influencing extraction efficiency were optimized, making MDSPE time-saving (5 min) and organic-reagent-saving (2 mL). The M-COF can reutilize more than 8 times. After being quantified by LC-MS/MS, good linear relationships (determination coefficient of R2 > 0.9990) were obtained. The LODs were in the range of 0.01-0.05 μg/kg. The recoveries ranged from 76.4 to 112.5%. Both intra- and inter-day precision were less than 15%.