Study on standard of safe application of thiamethoxam on GAP of Lonicera japonica / 中国中药杂志

ABSTRACT

The paper is aimed to establish a method of residue analysis for thiamethoxam and to study its degradation dynamic and final residue and its standard of safe application of thiamethoxam on Lonicera japonica. Samples extracted with methanol by ultrasonication were purified with dichloromethane by liquid-liquid extraction and SPE column and analysed by HPLC-UV. The results showed that average rate was 84.91%-94.44% and RSD 1.74%-4.96% with addition of thiamethoxam in respectively diverse concentration, which meets inspection requirement of pesticide residue. Two kinds of dosages of thiamethoxam were treated- varying from recommended dosage (90 g x hm(-2)) to high dosage (135 g x hm(-2)), Results of two years test showed that thiamethoxam was degraded more than 90% seven days after application and the half - life period of thiamethoxam was 1.54-1.66 d. The digestion rate of thiamethoxam was fast in the L. japonica. The recommended MRL of thiamethoxam in the L. japonica is 0.1 mg x kg(-1), the dosage of 25% thiamethoxam WDG from 90-135 g x hm(-2) is sprayed less than three times a year on L. japonica and 14 days is proposed for the safety interval of the last pesticide application's and harvest's date.