Rapid, low temperature synthesis of molecularly imprinted covalent organic frameworks for the highly selective extraction of cyano pyrethroids from plant samples.

ABSTRACT

New imine-linked molecularly imprinted covalent organic frameworks (MICOFs) were successfully prepared, using fenvalerate as the dummy template. Schiff base reaction between 1,3,5-tris(4-aminophenyl)benzene and 1,3,5-triformylphloroglucinol was rapidly achieved at room temperature, using Sc(OTf)3 as the catalyst. The surface groups and morphologies of MICOFs were assessed by Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller surface area analysis, and scanning electron microscopy. The MICOFs exhibited high selectivity toward four structurally similar cyano pyrethroids, including fenvalerate, flucythrinate, ß-cyfluthrin and λ-cyhalothrin. A method based on solid phase extraction using MICOFs coupled to high performance liquid chromatography was established for the determination of cyano pyrethroids in plant samples. Linearity in the range 0.1-200 ng g-1, with correlation coefficients of 0.9981-0.9993, was obtained for the four cyano pyrethroids. Detection limits and quantification limits were in the range 0.011-0.018 ng g-1 and 0.036-0.060 ng g-1, respectively. Recoveries at three spiked levels ranged from 94.3% to 102.7%. The developed method is thus a promising technique for the selective extraction of cyano pyrethroids from complex matrices.