Synthesis of a novel core-shell magnetic covalent organic framework for the enrichment and detection of AFM1 and AFM2 in milk and dairy products using HPLC-MS/MS

• A novel magnetic COFs was prepared by grafting TPBD-BTA on Fe 3 O 4 t to enrich aflatoxins. • The as-prepared magnetic COFs exhibited remarkable adsorption capacity to enrich aflatoxins. • MSPE was combined with HPLC-MS/ MS to quantify trace aflatoxins. • The method was effectively used for analysis of milk and dairy products. Magnetic covalent organic framework nanocomposite denoted as Fe 3 O 4 @TPBD-BTA with core-shell structure was fabricated via a simple template-mediated precipitation polymerization method at mild conditions. The polyimine network shell was created through the polymerization of N,N,N′,N′-tetrakis(p-aminophenyl)-p-phenylenediamine (TPBD) and biphenyl-3,3′,5,5′-tetracarbaldehyde (BTA) in tetrahydrofuran (THF) by the Schiff-base reaction. Featuring with large good solution dispersibility, and high stability, the obtained Fe 3 O 4 @TPBD-BTA exhibited high adsorption capacities and fast adsorption for zearalenone and its Aflatoxin (AFT). The adsorption isotherms showed multilayer adsorption dominated at low concentration and monolayer adsorption at high concentration between the interface of AFs and Fe 3 O 4 @TPBD-BTA. With the Fe 3 O 4 @TPBD-BTA as sorbent, a magnetic solid-phase extraction-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was established for simultaneous adsorption and detection of five ZEAs in complex samples. The proposed method displayed favorable linearity, low limits of detection (0.006 5 − 0.008 2 μg/kg). The developed method has been applied for real sample analysis, with recoveries of 81.0%−109.6%. These results showed that Fe 3 O 4 @TPBD-BTA has a good application potential for the adsorption of AFs in milk and dairy products.