The Stability Of Tebufenozide And Its Degradation And Residual Regularity On Rice And Paddy Environment

In order to provide scientific evidence for the reasonable usage of Tebufenozide on rice, this paper studied the detection methods of Tebufenozide on rice, paddy water and soil, the stability of Tebufenozide pesticides, Tebufenozide standard solutions and Tebufenozide in rice samples, the degradation dynamics and residual regularity of Tebufenozide on rice and paddy environment in three provinces. The conclusions are as follows:(1) A robust method using HPLC has been established for determination of Tebufenozide in rice, paddy water, soil and so on.The limits of detection(LOD) of Tebufenozide in rice, paddy water, soil, plant and chaff was 0.02 mg/kg (mg/L). The average recovery of Tebufenozide in different samples ranged from 86.74% to 108.00%, the relative standard deviation(RSD) ranged from 0.41% to 4.42%. This method can be applied for the agricultural product quality monitoring department and the environmental monitoring department detectiong the residue of Tebufenozide in rice, paddy water, soil and so on.(2) The content of Tebufenozide in 4 different formulations all decreased over time after unsealed at normal atmospheric temperature.The stability showed as:20% Tebufenozide SC>34% Emamectin Benzoate-Tebufenozide WP>25% Emamectin Benzoate-Tebufenozide SC>10.5% Emamectin Benzoate-Tebufenozide EC. The result declared that 4 pesticides stored at normal atmospheric temperature are supposed to be used up in half year. When 0.1 mg/L,10 mg/L and 100 mg/L Tebufenozide standard solution were stored at normal atmospheric temperature and 4℃ separately, the content of Tebufenozide all decreased. The stability of Tebufenozide in standard solutions at 4℃ were better than those at normal atmospheric temperature, and the high concentration standard solutions were stabler than low concentration standard solutions. The result indicated that the low concentration standard solutions should not be used more than 3 days at normal atmospheric temperature,100 mg/L Tebufenozide standard solution should not be stored more than a year at -20℃. When the rice samples with Tebufenozide concentration of 0.2 mg/kg and 2 mg/kg were stored at -20℃,4℃ and normal atmospheric temperature, the residues of Tebufenozide all decreased over time with the rise of temperature. The result showed that, the residue of Tebufenozide in rice which as food can be reduced by storing at normal atmospheric temperature or extending the stoage time. While the rice as research samples should be stored at -20℃ and finish detecting in 2 months.(3) The simulation test was conducted to research the degradation dynamics of Tebufenozide in paddy water, soil and plant in three provinces from 2012 to 2013. The result showed that the degradations of Tebufenozide all conformed to first-order kinetic equation Ct=Coe～kt. The half-lives of Tebufenozide in paddy water, soil and plant were 1.67～6.28 d,4.50～12.60 d and 3.16～7.70 d, respectively. The experiment showed that Tebufenozide is a kind of pesticide that can be easily degradated.(4) The final residual experiment showed that, in natural condition of three provinces,20% Tebufenozide SC was applied in rice with the recommended dosage and method, the highest residue of Tebufenozide in rice that harvested more than 14 days after the last application was 0.0219 mg/kg, undoubtedly below the maximum residue limit(MRL) of rice in China(2 mg/kg).(5) According to the experiment results, it is suggested that the reasonable usage of 20% Tebufenozide SC on rice is 150 g/hm2(effective component of Tebufenozide is 30 g/hm2) with 750 L/hm2 water sprayed at most twice(a 7 days interval at least), and the safe interval is about 14 days.