Magnetic layered double hydroxide/zeolitic imidazolate framework-8 nanocomposite as a novel adsorbent for enrichment of four endocrine disrupting compounds in milk samples

Abstract

For the first time, a novel nanocomposite, zeolitic imidazolate framework/magnetic layered double hydroxide (Fe₃O₄@LDH/ZIF), was successfully fabricated through in situ synthetic method with Fe₃O₄ as magnetic core and composite as shell. The resulting materials were characterized by XRD, TEM, FT-IR, VSM, TGA and nitrogen adsorption-desorption analysis. The Fe₃O₄@LDH/ZIF was employed as a sorbent in dispersive micro-solid phase extraction (D-μ-SPE) for enrichment of four endocrine disrupting compounds (EDCs) from milk samples prior to ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) analysis. The synthesized nanocomposite showed bigger specific surface area and better absorption capacity than Fe₃O₄@LDH. The equilibrium adsorption capacities (Qe, mg/g) of EDCs on the Fe₃O₄@LDH/ZIF reached up to 47.4-138.8 mg/g, mainly resulting from hydrogen bonding, π-π interaction and electrostatic interaction between EDCs and nanocomposite. Several variables affecting the extraction efficiency were investigated and optimized. The method displays low limits of detection (3-15 ng L^-1), good linearity (10-5000 ng L^-1), acceptable precision (RSD < 7.8%) and accuracy (RE < 5.2%). Satisfactory repeatability was obtained with RSD in the range of 1.2-7.8%. This work provides a promising approach for the development of new sorbent media in sample preparation for the improvement of analytical performance.

Keywords: Dispersive micro-solid phase extraction; Endocrine disrupting compounds; Layered double hydroxides; Nanocomposite; UHPLC-MS/MS; Zeolitic imidazolate frameworks.