An Analytical Method For Residue And Degradation Dynamics Of Imidacloprid In Wheat

Imidacloprid is a new type of neonicotinoid insecticides that is first developed.It was registrated for pesticides by the U.S. environmental protection agency official in 1994. Imidacloprid is a new generation of chlorinated nicotine insecticide, widely used in crops, vegetables and fruit with broad spectrum, high efficiency, low toxicity, low residue, resistance of pests is not easy to produce, for people, animals, plants and natural enemies and safety etc, and have a tag, stomach toxicity and multiple absorption effect.In this paper,we do a research for the the residue analysis method and degradation rules to imidacloprid in wheat and soil,which to undersand the residue in wheat and the soil after the imidacloprid is used.A HPLC method was effective for detecting imidacloprid in wheat soil,plant and wheat grain. The samples be extracted by methanol,followed by a second extraction in petroleum ether and dichloromethane and then would be determined by HPLC with UV detector,with acetonitrile and water(23:77). The result showed that the spiked recoveries of wheat and soil were 82.03%~103.30% and the relative standard deviation(RSD%) between 2.22% and 10.61%(n=5) at the spiked concentration of 0.005 mg kg-1、0.05 mg kg-1 and 0.5 mg kg-1, respectively. Meanwhile, the recoveries and RSD% for the wheat straw were 78.93%~89.44% and 0.38%~11.00%, respectively. Minimum of detectable concentration of imidacloprid existing in the wheat and soil was 0.005 mg kg-1, and 0.01 mg kg-1 for the wheat plant. 600 g L-1 imidacloprid suspending agent was conducted in the wheat and soil from Tianjin, Shandong and Jilin province during 2012~2013. A two year field trial showed that was accordance with the kinetic equation. It was found that under field conditions, the dissipation half-lives of imidacloprid in wheat plant and soil was 3.8-8.5d and5.7-10 d, respectively. When the recommended dosage and 1.5 times recommended dosages of 600 g L-1 imidacloprid suspending agent was sprayed for 1-2 times at an interval of 7 d, the maximum residual concentration of propineb on the 14 st day after the last application is lower than the MRL of propineb in the apples according to standards of Ministry of Agriculture of China(0.05 mg / kg).This analysis method for the firse time used the UPLC method for the determination of imidacloprid in soil and wheat grain. The method is accurate, efficient and good repeatability.(NY1500-2007) of our country stipulates imidacloprid in wheat called simply MRL values is 0.05 mg/kg, recommendation 600 g/L imidacloprid suspending agent, control of wheat aphids, the highest dose of 9.0 g/mu, applying pesticide applying pesticide at most 2 times, is apart from the last 14 d, applying pesticide imidacloprid residues in wheat is safe.