Covalent organic framework-LZU1@PEI@Fe3O4-based magnetic dispersive micro-solid phase extraction of tetracyclines from environmental water prior to HPLC analysis

In this work, COF-LZU1@PEI@Fe3O4 was synthesized by immobilization of COF-LZU1 onto the surface of polyethyleneimine-functionalized Fe3O4 nanoparticles (PEI@Fe3O4) and employed as an adsorbent for magnetic dispersive micro-solid phase extraction of tetracyclines (TCs). COF-LZU1@PEI@Fe3O4 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 (R2) 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@Fe3O4 for efficient extraction and analysis of trace TCs in water samples.