Facile room temperature synthesis of a NiFe2O4-based magnetic covalent organic framework for the extraction of tetracycline residues in environmental water samples prior to HPLC.

In this study, a functionalized magnetic covalent organic framework (NiFe2O4@TAPB-TPA) was fabricated with NiFe2O4 nanoparticles as the magnetic core, and 1,3,5-tris(4-aminophenyl)benzene (TAPB) and terephthalaldehyde (TPA) as building blocks by a facile room temperature strategy. Benefitting from the π-π stacking and hydrogen bond interaction, NiFe2O4@TAPB-TPA showed great potential as a magnetic adsorbent for the extraction of tetracyclines (TCs). Under optimal conditions, good linearities (R2 > 0.9990) were obtained between the peak area and TC concentration in the range of 1-500 μg L-1 with limits of detection ranging from 0.09 to 0.26 μg L-1. The intra-day and inter-day relative standard deviations were less than 2.2% and 4.7%, respectively. The established method was successfully applied for the determination of TCs in diverse environmental water samples with satisfactory recoveries in the range of 91.6-102.7%. In addition, NiFe2O4@TAPB-TPA showed good reusability with the recoveries for TCs higher than 73.1% after nine recycles, indicating potential application of NiFe2O4@TAPB-TPA as an ideal adsorbent for the enrichment of TCs.