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.

中文翻译：

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基于共价有机骨架-LZU1@PEI@Fe3O4 的磁分散微固相萃取环境水体中四环素，然后进行高效液相色谱分析

在这项工作中，COF-LZU1@PEI@Fe ₃ O ₄通过将 COF-LZU1 固定在聚乙烯亚胺功能化的 Fe ₃ O ₄纳米粒子（PEI@Fe ₃ O ₄）表面上合成，并用作磁分散剂的吸附剂。四环素 (TC) 的微固相萃取。COF-LZU1@PEI@Fe ₃ O ₄通过扫描电子显微镜、傅里叶变换红外光谱、X 射线衍射和氮吸附-解吸等温线分析对其进行表征。最佳萃取解吸条件如下：15.00 mL样品溶液（pH 7.0）用5.0 mg吸附剂在30℃下萃取30 min，然后用1.50 mL甲醇/乙腈/0.02 mol L ^-1草酸溶液解吸(v/v, 1 : 2 : 7)。峰面积与 TC 浓度范围为 5–500 μg L ^-1之间获得了良好的线性，相关系数 ( R ² ) 高于 0.9992，检测限低于 0.51 μg L ^-1. 日内和日间的相对标准偏差 (RSD) 分别小于 5.7% 和 7.4%。该方法成功应用于环境水样中TCs的测定，回收率在87.0-113.8%范围内，RSD小于5.1%，表明COF-LZU1@PEI@Fe ₃ O ₄在高效提取和水样中痕量 TC 的分析。