Hyperbranched aromatic polyamide modified magnetic nanoparticles for the extraction of benzoylurea insecticides

Herein, a novel hyperbranched aromatic polyamide-coated magnetic sorbent was prepared by in situ polymerization on the surface of amino-functionalized Fe₃ O₄ nanoparticles. The magnetic sorbent was characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, elemental analysis, Brunauer-Emmett-Teller measurement, and X-ray photoelectron spectroscopy, etc. The new magnetic sorbent was used in the magnetic solid-phase extraction for the detection of seven benzoylurea insecticides. Under optimum conditions, low method detection limits (0.56-1.20 ng/mL), acceptable coefficient of determination (0.9967-0.9996), wide linear ranges (2.5-500.0 ng/mL), and good repeatability (intraday: 2.0-7.3%; interday: 1.9-9.2%) were achieved. The magnetic solid-phase extraction method based on the new magnetic sorbent showed good reliability in the analysis of seven benzoylurea insecticides in real water samples, as the relative recoveries were in the range from 80.1 to 116.3% with satisfactory RSDs (0.1-9.8%). By means of density functional theory and semiempirical quantum mechanical, the binding configuration and interaction energy of hyperbranched aromatic polyamide and benzoylurea insecticides were calculated. The result of theoretical calculation revealed that the adsorption of benzoylurea insecticides by hyperbranched aromatic polyamide was derived from hydrogen bonding and π-π stacking. The contribution of π-π stacking was greater than that of hydrogen bond, which was confirmed by energy decomposition analysis.