Mobility of Sulfosulfuron and Its Metabolite Aminopyrimidine in Soil under Laboratory Conditions
Leaching potential of sulfosulfuron and one of its metabolite aminopyrimidine in two different soils were studied under laboratory condition. The soils used were sandy clay with lower organic carbon content (1.25%) and clay loam having higher organic carbon content (5.5%). Sulfosulfuron and aminopyrimidine were sprayed on the surface of the soil column. The applied dosages are sulfosulfuron @ 25 g.a.i/ha, 50 g/ha, 100 g.a.i/ha and aminopyrimidine @ 5 g.a.i/ha, 10 g.a.i/ha, 20 g.a.i/ha. Collected the leachates from the columns every day after applying 60 mm of rainfall for a period of fifteen days. There after soil columns were cut in to cross sectional and analyzed for the residues of sulfosulfuron and aminopyrimidine at five cm difference in depth. A high performance liquid chromatography with Fluorescence detector was used for the quantification of residues. Limit of quantification for sulfosulfuron and aminopyrimidine was established as 0.001μg/ml. The recovery study conducted for Sulfosulfuron and aminopyrimidine at two different concentrations (LOQ and 10 × LOQ) showed mean recovery of 94.6%, 96.9% in water, 92.3%, 94.1% in Sandy clay soil and 89.2%, 90.0% in clay loam soil. Analysis of leachates collected from sandy clay soil columns showed the residues of sulfosulfuron 0.01 - 2.8 μg/ml and aminopyrimidine 0.005 to 0.76 μg/ml. Leachates collected from clay loam soil columns showed the residues of sulfosulfuron 0.001 to 0.10 μg/ml and aminopyrimidine 0.001 to 0.032 μg/ml. Sandy clay soil samples showed the residues of sulfosulfuron 0.01 to 0.09 μg/g and aminopyrimidine 0.001-0.012 μg/g and clay loam soil samples showed the residues of sulfosulfuron 0.002-0.50 μg/g and aminopyrimidine 0.006 to 0.04 μg/g. Leachates of soil columns applied with sulfosulfuron showed the residues of metabolites such as aminopyrimidine, desmethyl sulfosulfuron, substituted guanidine, rearranged amine and sulfonamide. Metabolites were confirmed by Electrospray tandem mass spectrometry (LC-MS/MS-ESI) analysis.
Chandran Loganayagi, and Atmakuru Ramesh