[Preparation of magnetic metal-organic frameworks-polydopamine for extraction and detection of cationic dyes from water samples in a fishery].

The catechol group of dopamine (DA) can chelate with the metal ion in the crystal of molecular organic frameworks (MOFs). Based on this principle, a magnetic metal polydopamine (PDA) framework (Fe3O4@Z67D) was prepared using ZIF-67 as the template, which was etched by DA, followed by polymerization of the DA monomers to form a PDA coating with a porous structure. The morphology, structure, and properties of the material were determined by various characterization methods. Fe3O4@Z67D was used as an adsorbent, and a magnetic solid-phase extraction/high-performance liquid chromatography method for the determination of two cationic dyes, methylene blue (MB) and crystal violet (CV), was established. Under the optimized extraction and detection conditions, the linear ranges for MB and CV were 0.5-200 μg/L and 0.01-50 μg/L, respectively, and the corresponding detection limits were 0.04 μg/L and 0.008 μg/L. The experimental results showed that the enrichment factors of Fe3O4@Z67D for the two dyes were 777 and 688, respectively. The extraction performance was largely unaffected even after the new material was reused 10 times. The method was applied successfully for the adsorption and detection of the above mentioned two dyes in fishpond water. The spiking recoveries of the two cationic dyes ranged from 82.0% to 109.0%, and the RSD was lower than 2.9%.