Preparation of amino-functionalized covalent organic framework modified Fe 3 O 4 nanoparticles for the selective enrichment of flavonoid glycosides

In this study, a surface functionalized Fe 3 O 4 composite with core–shell structure was fabricated based on Schiff-base and thiol-ene click reactions. The Fe 3 O 4 @COF@NH 2 magnetic nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectrometry, Fourier transform infrared spectroscopy, X-ray diffraction, Brunauer-Emmett-Teller and vibrating sample magnetometer. The material showed high specific surface area, high pore volume and satisfactory magnetism. Furthermore, the parameters for the extraction of four flavonoid glycosides, including the amount of adsorbent, adsorption time, pH value, adsorption temperature, ion strength, elution solvent and elution time, were investigated. While the adsorption capacity and adsorption mechanism were explored through static adsorption experiment, high adsorption capacity for rutin (31.6 mg/g), vitexin (36.7 mg/g), hyperoside (47.0 mg/g) and icariin (54.1 mg/g) were obtained based on the strongly π-π stacking, hydrogen-bonding and hydrophobic interactions. Furthermore, Freundlich model with higher R 2 value than Langmuir model, was more appropriate for fitting the isotherm adsorption. Finally, the material was applied for the separation, pre-concentration and analysis of four flavonoid glycosides in the fruit of Crataegus pinnatifida extract and rat plasma. Under the optimal conditions, the recoveries of spiked samples were between 89.2% and 106.5% with RSDs ranged from 0.2% to 6.2%. The results revealed a fast binding kinetics, high adsorption capacity, satisfactory selectivity, very good reusability and storage stability of the Fe 3 O 4 @COF@NH 2.