A magnetic covalent aromatic polymer as an efficient and recyclable adsorbent for phenylurea herbicides.

A magnetic covalent aromatic polymer (Fe3O4-NH2-CAP) was synthesized by grinding a covalent aromatic polymer (CAP) and amino-functionalized magnetic nanoparticles (Fe3O4-NH2 NPs). The CAP was prepared by a Friedel-Crafts reaction between biphenyl and 1,3,5-benzenetricarbonyl trichloride. The interaction in the Fe3O4-NH2-CAP is based on hydrogen bond formation between the carbonyl groups in the CAP and the amino groups in the Fe3O4-NH2 NPs. The adsorbent inherits the advantages of the CAP and also has the superior magnetic property of the Fe3O4 NPs. The adsorbent was applied to magnetic solid-phase extraction of six phenylurea herbicides (metoxuron, monuron, chlortoluron, isoproturon, monolinuron, buturon) from soil and water samples. Following elution with 600 μL methanol, the herbicides were quantified by HPLC. The calibration plots are linear in the 1.00-100 ng g-1 herbicide concentration ranges in case of spiked soil samples, and in the 0.10-40 ng mL-1 concentration range for spiked water samples. The limits of detection range from 0.3 to 0.5 ng g-1 (soil) and from 0.01 to 0.03 ng mL-1 (water), with relative standard deviations of <8.0% and < 6.9%, respectively. Graphical abstract Schematic presentation for the preparation of the magnetic covalent aromatic polymer (Fe3O4-NH2-CAP) and of magnetic solid-phase extraction.