Ionic liquid-modified magnetic covalent organic framework for the extraction of four pyrethroids in traditional Chinese herbs

Efficient enrichment of analytes and purification of matrices are crucial for the highly sensitive detection and monitoring of pesticides in traditional Chinese herbs. This work prepared magnetic ionic liquid-controlled covalent organic framework (IL-COF@Fe₃O₄) as the sorbent via a simple in-situ precipitation polymerization and thiolene "click" strategy. The IL-COF@Fe₃O₄ exhibited remarkable adsorption performance towards pyrethroids within 5 min. The adsorption of four pyrethroids on the surface of IL-COF@Fe₃O₄ was according with Langmuir model and pseudo-second-order kinetic model. The adsorption energies were theoretically calculated, which were permethrin>cypermethrin>fenvalerate>bifenthrin. The modification of ILs improved extraction capacity mainly because of the interaction of imidazole and Cl or F and the pore size effect. This method was developed for the rapid extraction of four pyrethroids in Codonopsis pilosula and Angelica sinensis. The linear range was 0.05-200 μg L^-1. Matrix effects were ranging from -16.14% to 9.53%, indicating the strong matrix anti-interference ability of IL-COF@Fe₃O₄.