Rearch On Residues And Dissipation Dynamics Of Difenoconazole In Rice Field

The residue analysis methods of difenoconazole in different rice matrices were established in this thesis.The samples were extracted by methyl alcohol,n-hexane and dichloromethane,then used distribution of liquid liquid extraction purification,finally detected by GC-ECD.The results showed that when the spiked levels ranged from 0.005 to 2.0 mg/kg,the recoveries of difenoconazole in rice matrices were ranged from 90.57%to 98.39%,the relative standard deviations were ranged from 1.45%to 4.84%,according with the pesticide residue test standards.The limit of detection for this method was 2.0×10-11 g,and the limit of quantification for rice plants,rice hull,rice,soil and paddy water were 0.02 mg/kg,0.02 mg/kg,0.02 mg/kg,0.02 mg/kg and 0.005 mg/kg,respectively.Through by rice field trials in Hunan,Zhejiang and Hebei provinces in 2014-2015,we studied the dissipation dynamics and final residues of the 40%difenoconazole SC in paddy field.The dissipation dynamics tests results showed that the digestion speed of difenoconazole in paddy water and plant were faster than that in soil.the degradation half-lives of difenoconazole in soil,paddy water and rice plants were 4.68-18.93d,0.81-6.3 1d and 2.74-5.68d,respectively.All the degradation half-lives were less than 30d,so difenoconazole was belongs to easily degradable pesticide.The final residues tests results showed that when the dosage of 40%difenoconazole SC was 120-180 g.a.i/ha,applying 3-4 times,applying pesticide interval for 7 days,recovery intervals for 7d,14d and 21d,the maximum residue of difenoconazole in all the rice samples in field trials was 0.0578mg/kg.