Residue And Degradation Dynamics Of Imidacloprid And Tricyclazole In Rice Straw

Using rice straw as fodder is one important way of its application. It is inevitable to use chemical pesticides in rice growth. Pesticide residues in straw may influence animal health and the safty of animal product. Detecting the concentration and the change of major pesticide residues can provide an important reference for utilization of straw feed and safety assessments.Imidacloprid is a neonicotinoid pesticide with the features of broad-spectrum, high efficiency, low toxicity and low residue. Pests are not easy to develop a resistance to it. Tricyclazole is a kind of medium toxicity fungicides within the strong suction. It can be quickly absorbed by all parts of rice. It is always used in preventing and curing rice blast. Both imidacloprid and tricyclazole are widely used in rice growth.This paper did research on the method for analysis of imidacloprid and tricyclazole residue in rice straw. And an analytical method for determining this two kinds of pesticide degradation dynamic and residues in rice straw and straw silage was established. The main results are as follows:1. Two different methods were applied and compared to extract and detect tricyclazole and imidacloprid in straw. The results indicated that, by using conventional method, a large amount of organic reagents were needed and low recovery rate was reached, at the same time it polluted the environment seriously. The results show that after extracted by methyl alcohol, the recovery of imidacloprid range is from 29.80%-42.52%,with RSD from 1.66%-12.38%.Using dichloromethane to extract imidacloprid, the results were between 57.39%-82.12% and the RSD were between 0.31-4.29%. The recovery of tricyclazole by use of methyl alcohol is 59.38%-62.25%, the RSD is 1.83%-8.71%.Compared to the conventional method, the improved method, using acetonitrile as the reagents, the recovery of imidacloprid is between 88.36% and 115.83%, the RSD range is 2.95%-21.93%, the recovery of tricyclazole is between 97.63% and 119.98%,the RSD range is 1.83%-12.38%.This method was more convenient and effective. The accuracy, reproductivity and precision of the method well satisfied the essential rules of pesticide residue determination.2 The result of degradation dynamic in rice straw indicated that:Using acetonitrile as reagents, purified with Supelclo ENVI-18 cartridges and dispersive solid phase adsorbents PSA, and determined by reversed phase column HPLC equipped with UVD.Two different methods were applied and compared to extract and detect tricyclazole and imidacloprid in straw.The residues degradation dynamics followed the first-order kinetic. Half-life of imidacloprid is 2.082d in Nanjing5055 and 1.905d in Zhendao No.10. Half-life of tricyclazole is 6.086d in Nanjing5055 and 5.66d in ZhendaoNo.10.Compared with tricyclazole, imidacloprid is more likely to degrade.The paper reported the final residue of imidacloprid and tricyclazole in rice straw. After sprayed the pesticide in recommended way in 30 days, the residue of imidacloprid is less than 0.7mg/kg, after 35 days, the residue of tricyclazole is less than 0.1mg/kg.Residues of imidacloprid and tricyclazole were lower than the maximum safe residual amount of EU rules after spraying 35 days, and thus the rice straw can be safely used as the fodder of herbivorous animals.3. The residue of imidacloprid and tricyclazole in silage rice straw indicated that:After ensilaging rice straw for 50days, the digestion rate of imidacloprid in Nanjing5055 is 6.61%-49.20% and 10.18%-59.56% in ZhendaoNo.10, the Digestion rate of tricyclazole in Nanjing5055 is 4.84%-52.43% and 8.33%-49.47% in ZhendaoNo.10. Compared with rice straw riped in nature, the digestion rate of ensilaged rice straw is lower than it.The ensilaging process can restrain the digestion rate of these two pesticide.