Fabrication of magnetic covalent organic framework for efficient extraction and determination of phthalate esters in milk samples

Using two monomers of 4,4″-diamino-p-terphenyl and 1,3,5-triformylphloroglucinol, a co-precipitation structured magnetic covalent organic framework adsorbent was fabricated. After that, a high efficient vortex-assisted magnetic solid-phase extraction method was developed prior to gas chromatography-tandem mass spectrometry analysis for the determination of phthalate esters in milk samples. The fabricated magnetic adsorbent was facilely fabricated, fully characterized, and exhibited high extraction efficiency, which can be attributed to its larger pore size as well as strong hydrophobic and π-π stacking interactions between adsorbent and phthalate esters. Key parameters affecting extraction efficiency were investigated. Under the optimized conditions, the proposed method possessed good linearity (3.0-1000 μg/L), high sensitivity (0.8-2.1 μg/L for limits of detection), and satisfactory recoveries (76.8-99.2%). The relative standard deviations for intra-day was 3.1-4.5% and inter-day was 3.3-6.1%. This work is suitable for high efficient separation/preconcentration of phthalate esters in milk samples.