Three-dimensional chitosan/graphene oxide aerogel for high-efficiency solid-phase extraction of acidic herbicides in vegetables

A simple, facile method was adopted to synthesize three-dimensional chitosan grafted graphene oxide aerogels modified silica (3D CS/GOA@Sil) as the eco-friendly, sustainable extraction material for the preconcentration of phenoxy acid herbicides. An amidation reaction realized the immobilization of CS and GO on the surface of silica, followed by the freeze-drying technique to yield the CS/GOA@Sil with 3D architecture structure. Successful synthesis and properties of 3D CS/GOA@Sil were characterized and confirmed by scanning electron microscope, infrared spectrum, BET adsorption-desorption analysis, thermalgravimetric analysis. The surface area of 3D CS/GOA@Sil was twice as much as that of the individual GO@Sil. Besides, the adsorption and extraction time were also shorter due to the ordered porous structure and rapid mass transfer. Under the optimal conditions, coupled with high-performance liquid chromatography-ultraviolet detector, this as-established method presented wide linearities with desirable correlation coefficients (≥0.9936) and low limits of detection (≤1.5 μg L-1). Finally, it was applied to analyze phenoxy acid herbicides in vegetables, and satisfactory relative recoveries of 62.38-102.92% spiked at standard solutions with different concentrations were obtained.