Simultaneous Determination of Residues of 11 Pesticides in Soil by Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry Coupled with QuEChERS Pretreatment

A method for simultaneous determination of residues of organophosphorus (dichlorvos, tricholorfon, dimethoate, and omethoate), carbamate (carbaryl, carbofuran, carbofuran-3-hydroxy, aldicarb, aldicarb-sulfone, and cldicarb-sulfoxide) and triazine (atrazine) pesticides in soil by ultra-high performance liquid chromatography-tandem mass spectrometry coupled with QuEChERS pretreatment was proposed. The soil sample (10.00 g) was taken, and 10 mL of water was added. The mixture was swirled and mixed well, and 15 mL of acetonitrile solution containing 1% (volume fraction) acetic acid was added for swirling for 2 min. QuEChERS extraction reagent was added, and the mixture was shaken vigorously for 5 min. After centrifuging for 5 min, an aliquot (5 mL) of the supernatant was placed into a centrifuge tube containing QuEChERS purifying reagent, and shaken vigorously for 5 min, After centrifuging for 5 min, an aliquot (1 mL) of the supernatant was blown to near dryness by nitrogen, and 10 μL of the mixed internal standard solution (2.0 mg·L^-1) was added. The mixed solution was made its volume up to 1.0 mL with 50% (volume fraction) methanol solution. After mixing well and filteration, the filtrate was taken to be determined. Accucore aQ column was used as the stationary phase, and 1% (volume fraction) formic acid solution containing 5 mmol·L^-1 ammonium acetate-methanol was used as the mobile phase system for gradient elution. The separated targets were ionized by electrospray ion source with positive ion mode, detected by multiple reaction monitoring mode, and quantified by internal standard method. As shown by the results, the linear ranges of the standard curves for 11 pesticides were 1.00-200.0 μg·L^-1, with detection limits in the range of 1.7-8.2 μg·kg^-1. Test for recovery was made on the blank soil sample at 3 concentration levels, giving results in the range of 58.7%-98.3%, and RSDs of the determined values were in the range of 0.51%-8.2%.