Study On Residue Analysis Methods And Residue Dynamic Research On 35% Endosulfan EC In Cotton

As a high efficiency Organochlorine insecticide, endosulfan is only pesticide that use in prevention cotton bollworm and cotton aphid. In agricultural production, endosulfan will take a key role in the future. In order to use endosulfan in science way, evaluate the residue level in cotton and affect in soil. In this paper, one-year residue-assignment of endosulfan was carried out in different Places. A method was studied for the analysis of endosulfan residue in cotton, cottonseed and soil and 35% endosulfan EC had been recommended to control cotton bollworm in cotton according to the results of field experiment.Residue analysis methods research on endosulfan, gas chromatography method has been used in cotton,cottonseed and soil, different methods have been compared by experiments. The results show, cotton and cottonseed sample were extracted with acetonitrile, after the extract was cleaned up with a Florisil column, endosulfan was analyzed by GC, the average recoveries of cotton ranged from 82.0% to 95.7%, the C.V was between 6.9% to 13%. The average recoveries of cottonseed ranged from 82.9% to 95.6%, the C.V was 3.2% to 20%. Soil sample was extracted with acetone, LLE by petroleum ether, the average recoveries of soil ranged from 87.6% to 104%, the C.V was between 6.2% to 21%. The pre-treatment method of samples and the chromatographic conditions of the analysis were critically examined in experiment, the above method were confirmed for its easier, exacter, faster and being better purification effect.Studies on residual degradation dynamics of endosulfan in cotton and soil were according to spraying once, sampling time after time. The results showed: in ShiJiaZhuang, the degradation curve equations of endosulfan in cotton and soil in different term and the degradation dynamics were: C_T=33.6e^-0.117T and C_T=2.38e^-0.0348T. The correlation coefficients were -0.9491 and -0.8368 and the half-lives were 5.92 and 19.92 days. In ChangSha, the degradation dynamics were: C_T=31.3e^-0.116T and C_T=9.20e^-0.0460T. The correlation coefficients were -0.8597 and -0.9521. The half-lives were 5.99 and 15.07 days. Residual degradation dynamics of endosulfan in different term in cotton and soil were all accorded with C=Coe-kt and all had high relativity. The degradation speed of endosulfan in cotton is fast than in soil and the degradation speed in ShiJiaZhuang is different from ChangSha.The final residues experiment: cotton were treated three and four times and interval of 14 days with the dosages of 945a.i.g/hm² and 1890a.i.g/hm² during the growing season of cotton. The application after harvest interval was 7 days. The result of final residues of endosulfan showed: in ShiJiaZhuang, the final residues of endosulfan in cotton were 0.492mg/kg to 13.2mg/kg. In cottonseed was not detectable, in soil was 0.196mg/kg to 0.851mg/kg. In ChangSha, the final residues of endosulfan in cotton was 0.421mg/kg to 1.58mg/kg, in cottonseed was not detectable,in soil was 0.114mg/kg to 0.258mg/kg. According to these data: there were positive relation between residue and consistence as well as times sprays for, the high of the concentration in usage and the more times of applying, the residual are more higher, and negative relation residue and the days from last application to harvest and the residual in cotton is above soil.Refer to FAO/WTO MRL endosulfan in cottonseed that MRL is 1.0mg/kg and our government prescribe the MRL in cottonseed is 1.0mg/kg. The result of the final residual showed: 35% endosulfan EC used on cotton is safe. The dosage of endosulfan applied on cotton is 945a.i.g/hm² to 1890a.i.g/hm² are all below limit standard and endosulfan in cottonseed was not detectable. So based on the result of the trial, we suggest that the dosage of endosulfan applied on cotton be 945a.i.g/hm² or 1890a.i.g/hm² and three or four times during the cotton growing period and MRL be 1.0mg/kg in cottonseed. The safe interval period should be 14 days. In this safe period, endosulfan is safe to environment and when harvest that the residual of cottonseed was not detectable and suitable the residual standard.