Application of urea-based magnetic covalent organic framework as sorbent for the determination of coumarin and its derivatives in food samples combined with liquid chromatography-mass spectrometry

A magnetic solid-phase extraction (MSPE) protocol using novel Urea-based magnetic covalent organic framework coupled with liquid chromatography-mass spectrometry was developed for the detection of coumarins in food samples (soft drink, biscuit and sesame paste). This adsorbent was synthesized through atom economic polymerization of tetrakis(4-aminophenyl) methane and 1,4-phenylene diisocyanate, which was successfully verified by a series of techniques. Major parameters influencing MSPE efficiency were optimized. This protocol had some advantages, such as organic-reagent-saving (2.0 mL), easy operating, short extraction time, and high repeatability (8 times). The established method exhibited superior linearity (R² ≥ 0.999) and the limits of detection ranging from 1.0 to 5.0 µg/kg. The recoveries of coumarin and its derivatives ranged from 73.8% to 113.5% and both intra- and inter-day precision were less than 15%. These data indicate the protocol is a highly promising alternative for coumarin extraction and enrichment.