Preparation of core-shell structured magnetic covalent organic framework nanocomposites for magnetic solid-phase extraction of bisphenols from human serum sample

Core-shell structured magnetic covalent organic framework (Fe 3 O 4 @COF) nanocomposites were synthesized via a facile approach at room temperature and explored as an absorbent for magnetic solid-phase extraction (MSPE) of bisphenols (BPs) from human serum sample. The as-prepared Fe 3 O 4 @COF nanocomposites with core-shell structure possessed high specific surface area (181.36   m 2 /g), uniform mesoporous size (~ 3.6   nm), high saturation magnetization (42.7   emu/g), and excellent thermal and chemical stability, rendering it as an ideal adsorbent with high adsorption efficiency and size selectivity. The experimental parameters influencing extraction efficiency, including adsorbent dosage, extraction time, pH and ion strength, desorption solvent and time, were investigated in detail. Taking these advantages together, a simple, fast, effective and sensitive method that MPSE followed by HPLC-MS, was proposed to detect five BPs, which exhibited good linearity (r > 0.9982) within the concentration ranges of 0.1–50   μg/L. Moreover, the low detection limits (1.0–78.1   ng/L), signal-to-noise ratio (S/N = 3), the high enrichment factors (56–95 fold), and good recoveries (93.0–107.8%) with relative standard deviations (RSDs) less than 3.4% for inter-day and 6.9% for intra-day were achieved. The developed method was also successfully applied to the analysis of trace BPs in human serum sample, which demonstrated the most promising potential of the Fe 3 O 4 @COF nanocomposites as good adsorbent in sample pretreatment.