Determination of Phenylurea Herbicide Residues in Environmental Water by High Performance Liquid Chromatography-Tandem Mass Spectrometry Coupled with Magnetic Solid Phase Extraction

The magnetic zeolitic imidazole ester material (Fe₃O₄@ZIF-8) was prepared by hydrothermal synthesis method, and was characterized by scanning electron microscope, transmission electron microscope and Fourier transform infrared spectrometer. 50 mg of Fe₃O₄@ZIF-8 was added to 100 mL of water sample, and the mixture was shaken at 40℃ for 10 min of adsorption. After Fe₃O₄@ZIF-8 was magnetically separated and the water sample was discarded, 0.5 mL of acetonitrile was added and the mixture was vortexed for 1 min for desportion, the eluate was transferred, and desorption was repeated three times. The combined eluate was dried by nitrogen blowing, the residue was dissolved with a mixed solution of methanol and 0.1% (φ) formic acid solution (6+4), and the volume of the solution was made up to 500 μL. After the solution was filtered through a 0.22 μm organic filter, the filtrate was seperated on an Agilent Zorbax Eclipse XDB-C₁₈ chromatographic column (50 mm×3 mm, 1.8 μm), with a mixture of methanol and 0.1% (φ) formic acid solution as the mobile phase for gradient elution. Electrospray ion source and multi-reaction monitoring mode were selected in mass spectrometry analysis. Linear relationships were found between peak areas of 4 phenylurea herbicides and the corresponding mass concentrations in the same range of 0.01-20.0 μg·L^-1, and the detection limits (3S/N) were in the range of 1.03-3.00 ng·L^-1. Test for recovery was made by standard addition method to blank sample, giving results in the range of 78.8%-106%, with RSDs (n=6) less than 7.0%.