| Chinese cabbage,kidney bean and grape hold an important place in production and consumption of fruits and vegetables in China.During the growth process of the crop,it is very important to use efficient and safe fungicides.Difenoconazole has protective,curative and eradicative effect in preventing and curing various fungal diseases.In view of our country's climate and soil characteristic,it is of great significance to assessing food security and environmental safety of difenoconazole.An analytical method was developed using a solid phase extraction(SPE) cleanup and gas chromatography with electron capture detector for the detection of the residues of difenoconazole in Chinese cabbage,kidney bean, grape and soil.It showed satisfactory validation parameters,such as accuracy, precision and sensitivity.The mean recovery of this method in Chinese cabbage ranged from 87.6%to 99.0%,in kidney bean ranged from 88.0%to 96.3%,in grape ranged from 85.7%to 98.4%,in soil ranged from 88.5%to 99.1%.The relative standard deviation(RSD)of this method in Chinese cabbage ranged from 1.7%to 10.5%,in kidney bean ranged from 2.5%to 5.5%,in grape ranged from 3.2%to 5.6%,in soil ranged from 1.6%to 4.8%.The applications of difenoconazole in Chinese cabbage,kidney bean, grape and soil were discussed to evaluate residue behavior and environmental safety of difenoconazole.In addition,the safety application standard was made.The main results were as follwes:1.According to the physichemical property of difenoconazole,gas chromatography was chosen as the detector.The best detecting condition for gas chromatography was determined after repeated tests,and the pre-treatment method was investigated.The Chinese cabbage,kidney bean and grape samples were extracted with mixture of acetone:dichloromethane(2:1,V/V), the soil samples were extracted after being socked overnight in acetone.Solid phase extraction was used as sample purification method,specifically as follows:the phenyl column(500mg,3mL)was used as the solid phase extraction column,3mL of the mixture of n-hexane/ethyl acetate(90:10,V/V) was used to remove the impurities,4mL of the mixture of n-hexane/ethyl acetate(60:40,V/V)was used to elute the samples.2.The results of residual dynamics showed that difenoconazole dissipated fast in Chinese cabbage,kidney bean and grape,while it dissipated slowly in soil.The half-life of difenoconazole was 6.6～7.8d in Chinese cabbage,8.3～9.7d in kidney bean,10.9～16.6d in grape,54.2～55.0d in the soil from Chinese cabbage field,100.5～111.8d in the soil from kidney bean field, 121.6～135.9d in the soil from grape field.The differences of climatic conditions and soil conditions led that the half-lives in soil were different.The dissipation rates of difenoconazole in Chinese cabbage,kidney bean,grape and soil all followed the first order kinetics.3.The results of the final residue assay indicated that the residue levels of difenoconazole in Chinese cabbage,kidney bean,grape and soil all increased as the application dosage and application times increased,or as the harvest interval decreased.4.Referring to the results of the final residue assay and other country's MRL,the MRL of Chinese cabbage was suggested to be 0.2mg/kg, difenoconazole should be applied on Chinese cabbage at the dosage of 52.5～75g/ha for 2～3 times with 10 days application interval,and the pre-harvest interval should be 28 days;the MRL of kidney bean was suggested to be 0.2mg/kg,difenoconazole should be applied on kidney bean at the dosage of 75～125g.a.i./ha for 3 times with 7 days application interval,and the pre-harvest interval should be 7 days;the MRL of grape was suggested to be 0.2mg/kg,difenoconazole should be applied on grape at the dosage of 75～125g.a.i./ha for 2 times with 10 days application interval,and the pre-harvest interval should be 14 days.Difenoconazole could be considered no pollution to the environment,and the use of difenoconazole could be safe and effective if difenoconazole was applied on the basis of the pre-harvest interval suggested in this paper.
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