Sensitive measurement of polycyclic aromatic hydrocarbons based on strong enrichment from magnetic covalent organic framework before high performance liquid chromatography analysis

In this study, a magnetic covalent organic framework composite (Fe3O4@COF-BTCA-TMB) was conceived and synthesized with benzene-1,3,5-tricarbaldehyde and 3,3',5,5'-tetramethyl benzidine as monomers. The modification of COF endowed the magnetic composite with a large number of functional groups and benzene rings, which exhibited high affinity to polycyclic aromatic hydrocarbons (PAHs) attributed to pi-pi conjugation and hydrophobic interaction. Based on these properties, it was utilized to conceive a highly efficient magnetic solid phase extraction method to enrich PAHs from water samples prior to high performance liquid chromatography analysis. The key factors that affect the extraction efficiencies of six PAHs in water samples were explored. Under the optimized conditions, six PAHs obtained good linearity in wide concentration ranges of 0.2-80 mu g L-1, 0.2-180 mu g L-1, and 0.2-240 mu g L-1, respectively. The limits of detection (LODs) ranged from 0.03 to 0.09 mu g L-1, and the enrichment factors were in the range of 107-149. The adsorption of PAHs on Fe3O4@COF was consistent with the quasi-second-order kinetic model, and Freundlich adsorption isotherm model. The conceived method was evaluated with real water samples and satisfactory recoveries (73.8 % similar to 100.5 %) were obtained, indicating that it was simple, robust and efficient, and could be optioned for monitoring trace PAHs in environment.