Residueanddissipationdynamicsofflubendiamidandbuprofezinin<italic>Zizanialatifolia</italic>byultraperformanceliquidchromatography-tandemmassspectrometry

A new method had been developed to determine flubendiamid and buprofezin residues in Zizania latifolia. Samples were extracted by acetonitrile, nitrogen blowing to near dry, dissolve with methanol and clean up with PSA, gradient elution with 0.1% formic acid and methanol, then positive ions electrospray scanning with multiple reaction monitoring mode, detection with ultra high performance liquid chromatography tandem mass spectrometry, external standard method of quantitative. When the spike levels of flubendiamid and buprofezin ranged from 0.005 mg/kg to 1 mg/kg, the mean recoveries varied from 81% to 107% with the coefficient of variation of 4.2%–11%, respectively. The dissipation dynamics of flubendiamid and buprofezin conformed to first order kinetics equation with the half-lives was 2.3 d and 2.8 d, respectively. Given that the half-lives was short, flubendiamid and buprofezin could be classcified as the easily degradable pesticide type. In the final residue trials, at the 7^th, 14^th and 21^th days after the last spraying, the final residues of 10% avermectin·flubendiamid SC and 25% buprofezin WP were determined after two and three applications at levels of 450–675 g/hm² and 600–900 g/hm². The results revealed that residues of flubendiamid was lower than 0.01 mg/kg and that of buprofezin varied from lower than 0.005 mg/kg to 0.078 mg/kg. In conclusion, when 10% avermectin·flubendiamid SC were sprayed on Zizania latifolia twice according to the recommended dose of 450 g/hm², the safety interval of buprofezin in Zizania latifolia could be set as 7 d．When 25% buprofezin WP were sprayed in Zizania latifolia twice according to the recommended dose of 675 g/hm², the safety interval of buprofezin in Zizania latifolia could be set as 21 d．