Covalent organic framework-LZU1@PEI@FeO-based magnetic dispersive micro-solid phase extraction of tetracyclines from environmental water prior to HPLC analysis

In this work, COF-LZU1@PEI@Fe 3 O 4 was synthesized by immobilization of COF-LZU1 onto the surface of polyethyleneimine-functionalized Fe 3 O 4 nanoparticles (PEI@Fe 3 O 4 ) and employed as an adsorbent for magnetic dispersive micro-solid phase extraction of tetracyclines (TCs). COF-LZU1@PEI@Fe 3 O 4 was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and nitrogen adsorption-desorption isotherms analysis. The optimal extraction and desorption conditions were as follows: 15.00 mL sample solution (pH 7.0) extracted with 5.0 mg of adsorbent for 30 min at 30 °C, and then desorbed with 1.50 mL methanol/acetonitrile/0.02 mol L −1 oxalic acid solution (v/v, 1 : 2 : 7). Good linearities were obtained between the peak area and TC concentration ranging from 5-500 μg L −1 with correlation coefficients ( R 2 ) higher than 0.9992 and limits of detection lower than 0.51 μg L −1 . The relative standard deviations (RSDs) of intra-day and inter-day were less than 5.7% and 7.4%, respectively. The developed method was successfully applied to the determination of TCs in environmental water samples with recoveries in the range of 87.0-113.8% and RSDs less than 5.1%, suggesting great potential of COF-LZU1@PEI@Fe 3 O 4 for efficient extraction and analysis of trace TCs in water samples. Schematic of the m-μ-dSPE-HPLC strategy for the extraction and detection of TCs.