The Research Of Testing Method And Residue Of Thiacloprid In The Cucumber And Soil

Thiacloprid is a new-kind of chlorinated nicotine pesticides, which has a good stomach poison with a great contact activity. Without the cross-resistance to convwntional insecticides, thiacloprid is a efficient pharmacy to prevent the sucking and chewing mouthparts.The pesticide is the essential method to guarantee the safe and ecnomical benefits of modern agricultural, but the appropriate amount of pesticides is important for the hunman healthy and eco-environmental safety. Cucumber is one of main vegetables, in which the resisdent of pesticides is very striking. In this paper, we study the analysis method and residue of thiacloprid in the cucumber and soil. Results are as follows:We established a sensitive and efficient solid-phase extraction (SPE)-high performance liquid chromatography (HPLC) detection method for the analysis of thiacloprid residues in the cucumber and soil. After ultrasonic extracted by acetonitrile, the soil and cucumber samples were purified by florisil SPE column, respectively. The quantification of the samples were performed by HPLC with a UV detector.Under the adding concentrations of 0.03～0.3mg/kg concentrations, the recovery rate of thiacloprid in the soil was 84%～90%, relative standard deviation (RSD) was 2.5% to 4.5%; in the cucumber was81% to 90%. The relative standard deviation (RSD) was 2.6% to 3.9%. This minimum detection limit (LOD) of this method is 6.0×10-10 g and the minimum detection quantity (LOQ) is 0.03mg/kg.Three field experiments were carried out in Beijing, Anhui and Hainan in2009and 2010,through which we study the dynamic and final residual of thiacloprid in the cucumber and soil. Residual dynamic test results showed the digestion dynamic equation of thiacloprid in cucumber:c=0.428e-0..25t (Beinjing), R2=0.993, the half-life is 2.8 days; c=0.491e-0.33t (Hainan), R2=0.950,the half-life is 2.1 days; c=0.439e-0.31t (Anhui),R2=0.985, half-life is 2.3 days; And those in soil were:c=0.182e-0.12t 12t(Beijing),R2=0.901,the half-lifeis 5.8days; c=0.137e-0.11t (Hainan), R2=0.878, the half-life is 6.3 days; c=0.182e-0.14t(Anhui), R2=0.928, the half-life is4.9 days; These data showed that the thiacloprid in cucumber was easily biodegradablely, the degradation rate was faster than the degradation rate in soil.The final residue test results showed that when the pesticide was sprayed at a rate of102.5～154 g (ai)/ ha,1～2 times with an application interval of 10days, the amount of thiacloprid residues in cucumber was less than 0.30mg/kg after 2day. Due to the lack of maximum permissible residue level (MRL) in cucumber in China, the thiacloprid MRL is set as 0.30mg/kg according to the CAC provisions..According to the research result the safe using interval period of 36% water- thiacloprid dispersible agent was 2days.