Core–shell-structured magnetic covalent organic frameworks for effective extraction of parabens prior to their determination by HPLC

Covalent organic framework (COF)–decorated magnetic nanoparticles (Fe 3 O 4 @DhaTab) with core–shell structure have been synthesized by one-pot method. The prepared Fe 3 O 4 @DhaTab was well characterized, and parameters of magnetic solid-phase extraction (MSPE) for parabens were also investigated in detail. Under optimized conditions, the adsorbent dosage was only 3 mg and extraction time was 10 min. The developed Fe 3 O 4 @DhaTab-based MSPE-HPLC analysis method offered good linearity (0.01–20 μg mL −1 ) with R 2 (0.999) and low limits of detection (3.3–6.5 μg L −1 ) using UV detector at 254 nm. The proposed method was applied to determine four parabens in environmental water samples with recoveries in the range 64.0–105% and relative standard deviations of 0.16–7.8%. The adsorption mechanism was explored and indicated that porous DhaTab shell provided π-π, hydrophobic, and hydrogen bonding interactions in the MSPE process. The results revealed the potential of magnetic-functionalized COFs in determination of environmental contaminants. Graphical abstract