Residues and decline study of azoxystrobin in soybean

A gas chromatography method was developed for determining azoxystrobin residues in soybean.The samples were extracted with acetonitrile,and cleaned up by glass column chromatography with Florisil and determined by gas chromatograph with electronic capture detector(GC-ECD).Results showed that the fortified concentration of azoxystrobin from 0.1 mg/kg to 2.0 mg/kg,the ranges of average recoveries and coefficient variation of the method were 93.4% to 101.1%,1.2% to 7.5% respectively.The limit of detection was estimated to be 1×10-12 g,and the limit of quantification was 0.025 mg/kg.With high dosage 337.5 g a.i./ha,the half-life of azoxystrobin was 0.8 to 3.6 days in the soybean plant.Soybean plant was treated for three and four times with the dosages of 225 g a.i./ha and 337.5 g a.i./ha,the results revealed that the azoxystrobin residues in soybean were all below the MRL of CAC(0.5 mg/kg).Recommended dosage 225 g a.i./ha of azoxystrobin 25% SC was suggested to apply in soybean,the MRL of azoxystrobin in soybean may be suggested to set at 0.5 mg/kg.It’s recommended that the preharvest interval of azoxystrobin in soybean set at 14 days,the maximum application times below three.