Preparation of hydrophilic carbon-functionalized magnetic microspheres coated with chitosan and application in solid-phase extraction of bisphenol A in aqueous samples

Hydrophilic carbon-functionalized magnetic microspheres coated with chitosan (Fe3O4@C@CHI) were synthesized for the first time. The hydrophilic carbonaceous layer on the Fe3O4 microspheres was formed by the hydrothermal reaction of Fe3O4 microspheres and glucose, and then chitosan was coated on surface of the carbon-functionalized microspheres by an easy zero-length reaction with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) as cross-linkers. The Fe3O4@C@CHI microspheres were spherical core–shell structure with uniform size at about 400 nm. The microspheres had a high saturation magnetization of 60.22 emu g−1, which was sufficient for magnetic separation. The Fe3O4@C@CHI microspheres presented good hydrophilic property due to the abundant carboxyl and hydroxyl groups on the carbonaceous layer of the microspheres. The successful modification of chitosan on the surface of carbon-functionalized magnetic microspheres was validated by the adsorption of Eriochrome Black T (EBT). The prepared microspheres were applied as magnetic solid-phase extraction materials for extraction of bisphenol A (BPA) in aqueous samples. The extraction recoveries of spiked samples were in the range of 99.4–102.6% with low relative standard deviations of 2.8–3.9%. The results demonstrated that the novel Fe3O4@C@CHI microspheres were good candidate as magnetic SPE materials for extraction of analytes from aqueous samples.