Preparation of magnetic nitrogen-doped porous carbon by incomplete combustion with solvothermal synthesis for magnetic solid-phase extraction of benzoylurea insecticides from environmental water.

In this work, magnetic nitrogen-doped porous carbon (Fe3O4@N-PC) was prepared via incomplete combustion coupled with solvothermal synthesis for extraction of four benzoylureas (BUs) insecticides. Among them, nitrogen-doped porous carbon was produced through incomplete combustion of filter paper loaded with mixture formed by Zn(NO3)2·6H2O and polyethyleneimine solution, and magnetic nanoparticles were further introduced by solvothermal method. Compared with magnetic porous carbon (Fe3O4@PC), the surface hydrophilicity of Fe3O4@N-PC was improved by virtue of the doping of nitrogen atoms, and the dispersion of Fe3O4 was more uniform, which greatly exposed the adsorption site. The characterization of Fe3O4@N-PC were carried out by TEM, XRD, elemental analysis, XPS, BET and magnetic hysteresis curve. Besides, Fe3O4@N-PC was successfully used as magnetic solid-phase extraction (MSPE) adsorbent, which showed excellent enrichment factors and extraction recoveries toward polar BUs insecticides due to the polar surface and introduction of Lewis-basic nitrogen. The optimum amount of Fe3O4@N-PC adsorbent, extraction time, pH value, desorption solvent, desorption time and PEI concentration for BUs insecticides extraction were determined to be 3 mg, 10 min, 8, acetone/acetic acid (19:1, V/V), 6 min and 60 g L-1, respectively. Under this experimental condition, the enrichment factors ranged from 182 to 192 with good intra- and inter-day relative standard deviations (RSDs). The calibration lines were linear over the concentration in the range of 1-800 μg L-1, the limit of detection (LOD) and limit of quantification (LOQ) were 0.3 μg L-1 as well as 1 μg L-1, respectively. The recoveries for spiked sample ranged from 90.7 to 107.3% in spiked Yellow River water with the RSDs less than 7.0%. The results showed that the established MSPE strategy based on Fe3O4@N-PC could be used for the detection of trace BUs in complex samples.