β‐Cyclodextrin‐modified three‐dimensional graphene oxide‐wrapped melamine foam for the solid‐phase extraction of flavonoids

A new three‐dimensional graphene oxide‐wrapped melamine foam was prepared and used as a solid‐phase extraction substrate. β‐Cyclodextrin was fabricated onto the surface of three‐dimensional graphene oxide‐wrapped melamine foam by a chemical covalent interaction. In view of a specific surface area and a large delocalized π electron system of graphene oxide, in combination with a hydrophobic interior cavity and a hydrophilic peripheral face of β‐cyclodextrin, the prepared extraction material was proposed for the determination of flavonoids. In order to demonstrate the extraction properties of the as‐prepared material, the adsorption energies were theoretically calculated based on periodic density functional theory. Static‐state and dynamic‐state binding experiments were also investigated, which revealed the monolayer coverage of flavonoids onto the β‐cyclodextrin/graphene oxide‐wrapped melamine foams through the chemical adsorption. 1 H NMR spectroscopy indicated the formation of flavonoids–β‐cyclodextrin inclusion complexes. Under the optimum conditions, the proposed method exhibited acceptable linear ranges (2–200 μg/L for rutin and quercetin‐3‐ O ‐rhamnoside; 5–200 μg/L for quercetin) with correlation coefficients ranging from 0.9979 to 0.9994. The batch‐to‐batch reproducibility ( n  = 5) was 3.5–6.8%. Finally, the as‐established method was satisfactorily applied for the determination of flavonoids in Lycium barbarum (Goji) samples with relative recoveries in the range of 77.9–102.6%.