Preparation and application of magnetic graphene oxide coated with a modified chitosan pH-sensitive hydrogel: an efficient biocompatible adsorbent for catechin

In the present study, graft copolymerization of acrylic acid sodium salt (AAS) onto O-carboxymethyl chitosan (O-CMCs) produced a highly hydrophilic and pH-sensitive hydrogel polymer of O-CMCs-g-AAS with a porous surface morphology. The grafted chitosan copolymer was coated on magnetic graphene oxide (MGO) and characterized with TEM, SEM, and FT-IR techniques. The prepared nanocomposite, [O-CMCs-g-AAS]/MGO, was successfully used as an efficient and biocompatible adsorbent in magnetic solid phase extraction (MSPE) coupled with gas chromatography-mass spectrometry (GC-MS) for preconcentration and determination of catechin in tea beverages. The influence of the main parameters affecting the quality of the coating process was investigated and optimized using a response surface methodology. Under the optimum conditions, the adsorbent demonstrated a satisfactory adsorption capacity (27 mg g(-1)) for catechin and good linearity in the range of 0.005-5 mu g mL(-1) with a determination coefficient (R-2) of 0.9987. The limit of detection (LOD) and limit of quantification (LOQ) were 0.001 and 0.003 mu g mL(-1), respectively. The relative standard deviation (RSD) was 4.1% (n = 5, C = 0.5 mu g mL(-1)).