Residue Analysis of Thifensulfuron-methyl and theResidue Dynamics in Corn Field

A SPE-HPLC-ESI(+)-MS method for the determination of thifensulfuron-methyl residues in soil,corn grains and plants was developed.Residue dynamics in soil and the final residues in soil,corn grains and plants were evaluated.The residue of thifensulfuron-methyl in samples (corn grains,plants and soil) was extracted by a mixture of acetonitrile and phosphate buffer (pH 7.8)=2∶ 8(V/V),vortex and ultrasonic,and then the extracts were adjusted to low pH and passed through a C18 solid phase cartridge under vacuum condition,the elution was concentrated under nitrogen,the determination and quantitation were performed by HPLC-ESI-MS.The minimum detectable amount of thifensulfuron-methyl was 0.2 ng,and the minimum detectable concentration of thifensulfuron-methyl in the samples of soil,corn grains and plants were 2 μg/kg. The average recoveries ranged from 77.9% ~100.4%,with variation coefficient from 1.6% ~6.5%.The results of two-year field trial showed that the half-lives of thifensulfuron-methyl in soil were in a range of 0.92 ~1.23 days.When the corn field was treated by thifensulfuron-methyl 75% WP at 33.3 g/hm2 ~50 g/ hm2(a.i.25 g/hm2~37.5 g/hm2) one time at corn 2 ~3 leaf growth period,the residues in soil,corn grains and plants were less than 2 μg/kg at 40 or 80 days after application.