A rapid and facile approach was developed for the synthesis of core-shell structured magnetic covalent organic framework nanobeads by using the monodisperse Fe₃O₄ nanoparticles (NPs) as magnetic core, and 1,3,5-triformylbenzene (Tb) and benzidine (Bd) as two building blocks (denoted as Fe₃O₄@TbBd), which were explored as an adsorbent for magnetic solid-phase extraction (MSPE) of estrogens from human urine sample. The core-shell structured Fe₃O₄@TbBd nanobeads showed some attractive features involving high specific surface area (202.18 m²/g), uniform pore size distribution (2.8 nm), high magnetic responsivity (41.4 emu/g), as well as excellent thermal and chemical stability, which made it an ideal adsorbent for selective isolation and enrichment of estrogens. Some parameters influencing extraction efficiency, including adsorbent dosage, extraction time, pH, ion strength, desorption solvent and desorption time were investigated systematically. Combined with HPLC–MS, a simple, fast, and sensitive method was developed for the enrichment and sensitive determination of seven estrogens, which showed good linearity (r > 0.9978) in the range of 0.005–10 μg/L, low limits of detection (0.2–7.7 ng/L, S/N = 3), low limits of quantification (0.6–25.6 ng/L, S/N = 10), high enrichment factors (75–197 fold), and good precision with relative standard deviations (RSD) lower than 4.8% for intra-day and 6.7% for inter-day. The proposed method was successfully applied to the analysis of trace estrogens in urine sample of pregnant woman with good recoveries (80.6–111.6%), demonstrating the promising potential of the Fe₃O₄@TbBd nanobeads as adsorbent in sample pretreatment.

通过使用单分散的Fe ₃ O ₄纳米颗粒（NPs）作为磁性核以及1,3,5-三甲酰苯（Tb）和联苯胺（ Bd）作为两个结构单元（表示为Fe ₃ O ₄ @TbBd），被研究用作从人尿液样品中磁性固相提取雌激素的吸附剂。核-壳结构的Fe ₃ O ₄ @TbBd纳米珠表现出一些吸引人的特征，包括高比表面积（202.18 m ²/ g），均匀的孔径分布（2.8 nm），高磁响应率（41.4 emu / g），以及出色的热和化学稳定性，这使其成为选择性分离和富集雌激素的理想吸附剂。系统地研究了影响萃取效率的一些参数，包括吸附剂量，萃取时间，pH，离子强度，脱附溶剂和脱附时间。结合HPLC-MS，开发了一种简单，快速，灵敏的方法来富集和灵敏地测定7种雌激素，在0.005–10μg/ L的范围内显示出良好的线性（r> 0.9978），检出限低（0.2–7.7 ng / L，信噪比= 3），定量下限低（0.6–25.6 ng / L，信噪比= 10），富集因子高（75–197倍），相对标准品的精密度高偏差（RSD）小于4。日内为8％，日间为6.7％。该方法已成功用于回收率高（80.6–111.6％）的孕妇尿液样品中痕量雌激素的分析，证明了铁的潜力巨大。₃ O ₄ @TbBd纳米珠作为样品预处理中的吸附剂。