Positively charged covalent organic framework and its application in the dispersive solid-phase extraction of ultraviolet-filters from food packaging material migrants

Covalent organic frameworks (COFs) show excellent property, such as high porosity and excellent structure stability and were well applied in fields such as catalysis and adsorption, but most of the COFs showed similar structure and thus similar adsorption performance. Modification of simple COFs to enhance its adsorption performance in separation technique is an important issue. In this study, quaternary ammonium groups with long hydrophobic chain were introduced into a simple COF (TpPa-1) for the first time. The positively charged COF (PC-TpPa-1) can form electrostatic interaction and hydrophobic effect with negatively charged analytes, and showed good adsorption performance for ultraviolet-filters (UV filters). Under the optimum conditions, i.e. adsorbent amount 20 mg, pH = 7, 1.0 mL acetonitrile as eluent, the obtained recoveries for all UV filters were in the range of 86.4-96.7%.The developed method was successfully applied to the determination of UV filters from food packaging material migrants with the aid of HPLC as a detector.