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Method validation and residue analysis of methoxyfenozide and metaflumizone in Chinese broccoli under field conditions by liquid chromatography with tandem mass spectrometry.

Methoxyfenozide and metaflumizone are insecticides used on Chinese broccoli to prevent insects and increase yield. However, the residues are potentially harmful to the environment and consumers. In this study, the quick, easy, cheap, effective, rugged, safe method with HPLC-MS/MS was modified and validated for determination of methoxyfenozide and metaflumizone in Chinese broccoli. The clean-up efficiency of different sorbents including C18 , primary secondary amine, graphitized carbon black and carbon nanofiber were compared. Recoveries of the validated method were 71.8∼94.6% with relative standard deviations of 1.5∼3.2%, and the limits of quantification were 0.01 and 0.005 mg/kg for methoxyfenozide and metaflumizone, respectively. A storage stability test showed almost no degradation of methoxyfenozide in Chinese broccoli, however the degradation rates of metaflumizone was 22.9% after ten-week storage at -20°C. In field trials in four producing regions, the dissipation of both methoxyfenozide and metaflumizone in Chinese broccoli were fast, with half-lives of only 1.0∼5.1 and 0.7∼2.5 days, respectively. Terminal residues after application of the two pesticides were all below 1.0 mg/kg after 5 days. This article is protected by copyright. All rights reserved.