Simultaneous determination of bensulfuron-methyl and mefenacet residues in paddy field using high performance liquid chromatography

An analytical method of high performance liquid chromatography (HPLC) was established for the simultaneous determination of bensulfuron-methyl and mefenacet residues in paddy field (paddy water, soil and rice plant). The residues in the paddy water was extracted with methylene chloride, and the soil with alkaline mixed solution of acetonitrile-methylene chloride (1:1, v/v). The rice plant was extracted with alkaline methylene chloride which was cleaned up by a Florisil column. The separation was performed on a stainless steel C18 column (150 mm x 4.6 mm, 5 microm) at 30 degrees C by HPLC with an ultraviolet detector (UVD) at 238 nm, and water-methanol (30:70, v/v) as the mobile phase at a flow rate of 0.5 mL/min. The quantification was performed by external standard. The calibration curves were linear between the peak area and the concentration in the range of 0.05-5.00 mg/L for bensulfuron-methyl and mefenacet, and the correlation coefficients were more than 0.999 9. The average recoveries of the two herbicides spiked in the paddy water, soil and rice plant at the three concentration levels of 0.05, 0.10 and 1.00 mg/kg ranged from 85.39% to 113.33% with the relative standard deviations of 0.91%-10.24%. The method is characterized by simplicity, sensitivity and accuracy.