Simultaneous Determination of 5 Substituted Urea Herbicides in Soil by Gas Chromatography-Tandem Mass Spectrometry

A method for the simultaneous determination of 5 substituted urea herbicides including linuron, isoproturon, fluometuron, diuron and pencycuron in soil by gas chromatography-tandem mass spectrometry was proposed. 10 g of the ground and sieved soil sample was soaked with 10 mL of water, and extracted with 20 mL of acetonitrile and one bag of QuEChERS extractant containing 4.0 g of magnesium sulfate and 1.0 g of sodium acetate. 10 mL of the supernatant was transferred to 25 mL QuEChERS purification tube (containing 1 g of magnesium sulfate, 500 mg of N-propylethylenediamine and 500 mg of C₁₈ adsorbent) for vortex and centrifugation. 5 mL of the supernatant was taken and blown to nearly dry with nitrogen in water bath at 50℃, and then the residue was redissolved with 1 mL of acetone. The obtained solution was passed through 0.22 μm microporous membrane. The filtrate was injected into gas chromatograph with Rxi-5sil MS column as stationary phase, and separated under temperature programmed conditions. The targets separated was detected by triple quadrupole tandem mass spectrometer with electron impact ion source and multiple reaction monitoring mode, and quantified by external standard method. It was shown that linear relationships between values of mass concentration and peak area of linuron, isoproturon, fluometuron, diuron and pencycuron were kept in the range of 0.02-5.0 mg·L^-1, with detection limits (3S/N) in the range of 0.008-0.015 mg·kg^-1. Test for recovery was made on blank soil sample, giving results of in the range of 87.2%-102%, and RSDs (n=6) of the determined values were ranged from 1.8% to 3.5%. This method was applied to the analysis of actual samples, diuron and pencycuron were detected in soybean planting soil and vegetable planting soil, respectively.