Preparation of magnetic mesoporous metal-phenolic coordination spheres for extraction of crystal violet and leuco-metabolites in fish

To address the undesirably low porosity of phenolic resin, a new material termed magnetic mesoporous metal-phenolic coordination spheres (Fe3O4@Co-TA) was synthesized by chelating tannic acid (TA) with metal ions. Fe3O4@Co-TA was characterized by transmission electron microscopy, scanning electron microscopy, hysteresis loop (B-H) analysis, Fourier-transform infrared spectroscopy, and N2 adsorption-desorption. The results indicated that the new material comprises mesopores (2 nm and 3 nm) and exhibits a good magnetic response (44 emu/g). Combined with high-performance liquid chromatography (HPLC), a novel method for the detection of crystal violet (CV) and leucocrystal violet (LCV) by magnetic solid-phase extraction was established. Under the optimal extraction conditions, the linear ranges of CV and LCV detection were 0.2‒60 μg/L and 0.04‒40 μg/L, the detection limits were 0.04 μg/L and 0.008 μg/L, and the enrichment factors were 435 and 460, respectively. Fe3O4@Co-TA was reused ten times without significant reduction of the extraction ability. This method was successfully used for the detection of CV and LCV in fish samples, providing an effective technique for food safety monitoring and quality control.