Studies On Determination And Degradation Of Azoxystrobin Residue On Cucumber And In Soil

This paper firstly reported the method of determination of residual azoxystrobin on cucumber and in soil in China. The sample were extracted with acetone, partitioned by dichloromethane, cleaned up by passing through a silica-charcoal column, eluted with mixture of dichloromethane:ethyi (v/v, 7:3), and determined by capillary gas chromatography with NPD. The minimum amount of detection was 6.25 × 10-11g, and the minimum concentration of detection in cucumber and soil were 0.00125 mg.kg-1 and 0.00283 mg.kg-1,respectively. The average recoveries of azoxystrobin in cucumber and soil were 89.26%-94.94% and 90.03%-96.34%, respectively. The coefficients of variation ranged from 4.04%-5.54% and 3.57%~7.2%.Residual trial of azoxystrobin were conducted in Guangxi Nanning and Shanghai during 2003 - 2004.The result showed that under applied level of 270g(a.i)/ha,the half-life of azoxystrobin was 3.86-4.52 days in cucumber and 18.44-32.76 days in soil. The degradation kinetics of azoxystrobin in cucumber and soil accord with the first-degree reaction pattern.Cucumber plant were treated three and four times and interval of 7 days with the dosage of 180 g(a.i)/ha and 270 g(a.i)/ha during the growing season of cucumber.The residue of azoxystrobin in cucumber were 0.03924-0.2135mg.kg-1 in Guangxi Nanning and 0.0172 mg.kg-1-0.1826mg.kg-1 in Shanghai, in soil were 0.2032 mg.kg-1-0.9456 mg.kg-1 in Guangxi Nanning and 0.2050 mg.kg-1 -1.3997 mg.kg-1 in Shanghai afer the last application 1,3, 5 and 7 days . There were positive relation between residue and amount as well as times sprays for, and negative relation between residue and the days from last application to harvest.Azoxystrobin is a fungicide come from foreign. Our government has not formulatedthe rules of application and MRL on cucumber. Based on the result of the trial and refer to American MRL, we suggest that the dosage of azoxystrobin applied on cucumber be 180 g(a.i)/ha~270 g(a.i)/ha and four times during the cucumber growing period, and MRL be 0.3 mg.kg-1 in cucumber.