Simultaneous determination of pyrazosulfuro and mefenacet residues in rice and paddy field by high performance liquid chromatography

An analytical method of high performance liquid chromatography was established for simultaneous determination of pyrazosulfuro and mefenacet residues in paddy soil,water,unpolished rice and plant.Different solutions were used to extract the residues based on their source.The residues in water was extracted with methylene chloride;in paddy soil extracted with acidic methanol;in unpolished rice extracted with acidic acetone first,and further extracted with methylene chloride;in plant extracted with acidic mixed solution of acetonitrile-methylene chloride(volume ratio 1∶1) first,and the extraction was further purified with Florisil chromatography column.The separation was performed with a C18 column(4.6 mm×150 mm,5 μm),The flow rate of the mobile phase was 0.6 ml/min and column temperature was 30 ℃.Pyrazosulfuro and mefenacet were detected at uv wavelength of 240 nm with a mixed mobile phase consisted of water,methanol and acetic acid(volume ratio 70.0∶29.7∶0.3).This method could determine pyrazosulfuro and mefenacet residues in paddy field with a good linear relationship(R2=0.999 7–0.999 8) on the condition that the concentration of pyrazosulfuro and mefenacet changed from 0.01 mg/L to 1.00 mg/L.The limit of detection for the two ingredients were both 0.01 mg/kg,and their average recoveries ranged from 84.00% to 104.07% with a relative standard deviation at 8.55% below.This method,meeting the technical requirements for the determination of pesticide residue,could be applied to the detection and analysis of pyrazosulfuro and mefenacet residue in rice and paddy field.