Amino-functionalized Fe₃O₄-based covalent organic framework for efficient magnetic solid-phase extraction of three illegally added phosphodiesterase-5 inhibitors in functional food

The illegal addition of phosphodiesterase-5 (PDE-5) inhibitors in functional food poses significant food safety risks and health issues, requiring a sensitive and effective enrichment and detection method. Herein, a magnetic COFs (Fe 3 O 4 @TpDBA) was prepared by a layer-by-layer growth strategy. TpDBA was synthesized through the condensation of 1,3,5- Triformylphloroglucinol (Tp) and 4,4′-diamino-(1,1′-biphenyl)-3,3′-dicarboxylic acid (DBA). Fe 3 O 4 @TpDBA was used as an adsorbent for magnetic solid-phase extraction (MSPE) of PDE-5 inhibitors (sildenafil, tadalafil, and vardenafil), which enabled their efficient enrichment within 2 min. The lower binding energy value obtained through molecular docking calculations indicates stronger binding ability. The prepared Fe 3 O 4 @TpDBA exhibited high chemical stability (resistant to acid, alkali and organic reagents) and good reusability (10 adsorption/desorption cycles). Coupled with high-performance liquid chromatography-tandem mass spectrometry, Fe 3 O 4 @TpDBA-MSPE exhibited great potential in PDE-5 inhibitors. The developed method was optimized and validated, exhibiting a wide linear range and low limits of detection. Moreover, it was successfully applied to the determination of three PDE-5 inhibitors in five functional foods.