| 1. Chlorpyrifos-chlorfluazuron EW is a new pesticide which is a mixture of chlorpyrifos and chlorfluazuron.In this paper,a method of residue analysis was developed for determination of chlorfluazuron in cabbage and soil.Through field experiments in 2007 and 2008,Hefei and Beijing, the residue of chlorpyrifos and chlorfluazuron in cabbage and soil were investigated.On the basis of the field experiments,laboratory test was satarted on photo-degradation of chlorfluazuron.The photolysis of chlorfluazuron on glass surface was observed under high pressure mercury lamp by different treatment of chlorfluazuron alone and mixed with chlorpyrifo.It provides a scientific basis for its rational use in the field.2. The method of analysis residues of chlorfluazuron in the cabbage plants was established,on the base of comparing the system of extraction and purification.Samples were extracted with ethyl acetate,cleaned up by Florisoil column,and determined by HPLC.At three spiked levels (0.05,0.5,2 mg/kg),the recoveries of chlorfluazuron ranged from 81.95% to 97.78%,with the coefficient of variation in the range of 2.37% to 6.21%.The limit of detection was 1.2 ng,the limit of quantification was 0.02 mg/kg.Soil samples were extracted with acetone,and detected by HPLC.In 0.05~1 mg/kg range.the average recovery was 77.60 ~ 80.17%,the coefficient of variation was 3.29 ~ 5.17%.Each indicator is in line with the guideline on pesticide residue trials.The method is sensitive,simple,economical and practical,and applicable to testing the residue of chlorfluazuron in cabbage and soil.3. Chlorpyrifos in cabbage and soil Samples were extracted with ethyl acetate,determined by flame photometric detector of GC.The add concentration of chlorpyrifos was 0.01~1.0 mg/kg,the recovery rate of cabbage was 78.43~3.28%,and the coefficient of variation was 6.38 ~ 12.86%.The recovery rate of soil was 90.65 ~ 93.93%,and the coefficient of variation was 9.58 ~ 11.03%.The limit of detection was 1.5×10-11 g,and the limit of quantification was 0.01 mg/kg.Each indicator is in line with the guideline on pesticide residue trials.4. Dynamic degradation of chlorpyrifos-chlorfluazuron EW in 2007,2008 years,Hefei and Beijing was measured by the methods mentioned above.The residual test results of cabbage plants are as follows:half-life of chlorpyrifos is 2.41 d,1.4 d and 1.92 d in 2007,2008 of Hefei and 2008 of Beijing.Half-life of chlorfluazuron is 5 d,2.19 d and 2.28 d in 2007,2008 of Hefei and 2008 of Beijing.The residual test results of soil are as follows:half-life of chlorpyrifos is 4.33 d,3.48 d and 1.38 d in 2007,2008 of Hefei and 2008 of Beijing. Half-life of chlorfluazuron is 1.57 d,1.45 d and 5.75 d in 2007,2008 of Hefei and 2008 of Beijing.From the above results , we can see that the degradation speed of Chlorfluazuron-Chlorpyrifos EW is slowest in cabbage and soil by year of 2007.The residues and degradation speed are different in Hefei and Beijing.The cabbage harvest after 7d is more safety,if application of pesticides reasonably.5. Studied the photodegradation rate of chlorfluazuron under different initial concentrations and the photodegradation effect while mixed with chlorpyrifo under HPML.It provides a theoretical basis for its rational use in the field and environmental safety evaluation. Test results are as follows: the half-life is 1.61 h,4.57 h,17.68 h,21.79 h,46.82 h,when initial concentrations of chlorfluazuron is 0.0526,0.2632,0.5263,1.0526 , 2.6316μg/cm2 . It shows that there is a linear relationship between photodegradation rate and initial concentrations of chlorfluazuron on glass plate.The higher the initial concentration is,the slower the degradation rate.When the dose ratio of chlorfluazuron and added chlorpyrifos is 1:0,1:0.1,1:0.25,1:0.5,1:1,1:2,half-life of chlorfluazuron is 17.68 h,17.72 h,19.25 h,21.46 h,23.57 h,28.06 h.The results showed that the adding of chlorpyrifos inhibit on photodegradation of chlorfluazuron,and the greater the adding concentration,the inhibition is more obvious.
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