Pymetrozine Residues In Rice Growing Environment

Pymetrozine,4,5-dihydro-6-methyl-4-(3-methyl-amino pyridine)-1,2,4-3 (2H)-ketone, was a novel selective insecticide whose basic structure is a pyridine. It was discoveried and developed by Novartis in Swiss. Pymetrozine kill pests very quickly because of contact action and the absorption activity, so can be used for foliar spray and soil treatment. According to reports, Japan, EU and other developed countries has been developed maximum residue limits (MRL) of pymetrozine in rice, but China has not yet developed. Therefore, in August 2009～March 2011, the authors develop a systematic study about pymetrozine residues in rice and environmental media, by the method of combining laboratory and field trial, in order to assess the NMRs and work out the reasonable application guidelines and the proper used in rice fields. The main results are as follows:First of all, a quantitative high performance liquid chromatography method has been developed for the determination of Pymetrozine residues in rice using photodiode array detector. The analysis was performed on a C18 stainless steel column (200mm×5.0 mm i.d.) with mixture of methanol-water (15:85, V/V) as the mobile phase. The limit of detection was 0.02 mg/kg for Pymetrozine (S/N=3). The average recovery of five spiked concentration levels for Pymetrozine in Rice plant, rice chaff, brown ricewere 90.47%～97.95%,93.40%～100.38% and 95.22%～99.44%, respectively. The relative standard deviation (RSD) was 1.57%～3.49%,1.07%～2.00% and 1.32%～2.40% respectively. The results indicated that the method was fast, sensitive, simple, reproducible and practical for the residue detection and analysis of Pymetrozine in aquatic systems.Secondly, a quantitative high performance liquid chromatography method was established for the determination of Pymetrozine in rice growing environments.At the concentration range from 0.02 mg/kg to 2.00 mg/kg, the average recoveries of Pymetrozine in soil and water were 85.35%～90.84%,94.30%～96.92%, respectively. The corresponding relative standard deviation (RSD) was 4.35%～9.28%, 2.57%～5.61%, respectively. The results indicated that the method accords with demands of residue analysis of pesticide.Finally,with the mentioned method, dissipation dynamics and the terminal residues of Pymetrozine in rice, water and soil had been studied in Hunan and Henan. The results indicate that the degradation of rice, water and soil was in accordance with the regression equation. The results showed that:The degradation of Pymetrozine in rice, water and soil were followed first-order kinetic equation, its degradation was rapid and it belongs to the easy degradation pesticides.