Zeolitic imidazolate framework-8 coated Fe3O4@SiO2 composites for magnetic solid-phase extraction of bisphenols

Abstract

In this study, a new magnetic composite material zeolitic imidazolate framework-8 coated Fe₃O₄@SiO₂ (Fe₃O₄@SiO₂/ZIF-8) was prepared by in situ growth of ZIF-8 on the surface of Fe₃O₄@SiO₂ microspheres at room temperature. In addition, it had a large surface area, high superparamagnetism and great adsorption capacity. As is well known, MOFs have extraordinary adsorption capacity. As one of the classic MOFs, ZIF-8 has open metal sites, hydrophobic properties, and especially excellent water stability. Fe₃O₄ is generally used for the synthesis of different magnetic materials, which can make the preconcentrated material easy to separate from the extraction medium. All these features make the composite material Fe₃O₄@SiO₂/ZIF-8 suitable to be developed as an adsorbent for preconcentration of bisphenols (BPs) including bisphenol F, bisphenol A, bisphenol B and bisphenol AP. Most of all, applying Fe₃O₄@SiO₂/ZIF-8 to magnetic solid-phase extraction (MSPE) coupled with high performance liquid chromatography (HPLC) for detection of BPs can greatly improve the sensitivity of the method, and the process is simple and convenient. Under the optimal conditions, four BPs were detected with large linear ranges (0.05–200 μg L⁻¹), low limits of detection (LODs) (10–15 ng L⁻¹), relative standard deviations (RSDs) ranging from 2.0 to 4.5% and enrichment factors (EFs) ranging from 110 to 186. Additionally, the proposed method was applied to detect BPs in water and plastic packagings of food and drinks generally used in daily life.