Residue decline dynamics of propisochlor in corn and soil

The residue decline dynamics and final residues of propisochlor in soil,corn plant,corn samples were determined by gas chromatography equipped with μ-electron capture detector(GC-μECD).Samples were extracted with petroleum/ether-acetone (1∶1,V/V),and then cleaned up by liquid-liquid extraction and Florisil column,followed by detection with GC-μECD.With fortified concentration of 0.011 to 1.1 mg/kg,the recoveries ranged from 78.8% to 96.4% for corn and relative standard deviations of 0.54% to 10.5%.The limit of quantification was 0.011 mg/kg for soil,corn plant and corn.The half-lives of propisochlor in soil and corn plant were 4.7-5.3 days and 4.1-4.5 days for year 2009,5.4-5.5 day and 4.9-5.4 days for year 2010,respectively.When sprayed once at maize stem leaf with application rate of 2 400 g(a.i.)/ha and 3 600 g(a.i.)/ha, at the milk stage and maturity of corn,the final residues of propisochlor in corn were lower than LOQ.At harvest time (45 days after the treatment),propisochlor residues in soil and corn were lower than the reference MRL,indicating that use pattern of 900 g/L propisochlor EC on maize is acceptable.