Analysis of fluazinam residue behavior in wax gourd by ultra performance liquid chromatography-tandem mass spectrometry

To study the dissipation rate and the final residue level of fluazinam in wax gourd, the dissipation dynamics and final residue trials of 500 g/L SC were carried out in Beijing, Shandong, Anhui, Hunan, Yunnan and Guangdong Provinces. Among them, dissipation dynamic trials were set up in Beijing and Anhui. Samples were extracted with acetonitrile, cleaned up by primary secondary amine (PSA), detected by ultra performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS), and quantified by external standard method. The results showed that, among the spiked levels of 0.01-1 mg/kg, the recoveries ranged from 89% to 109%, the relative standard deviations (RSDs) ranged from 2.8% to 12%, and the limit of quantification (LOQ) was 0.01 mg/kg. The half-lives of fluazinam on wax gourd were between 2.04 to 2.17 days in Beijing and Anhui, respectively. The final residue trials in six provinces showed that the residue level of fluazinam on wax gourd was between <LOQ and 0.048 mg/kg. According to the results, the recommended application of 500 g/L fluazinam SC to prevent wax gourd downy mildew was three times at the dose of 250 a.i.g/hm² with a safe interval of 7 days from the harvest.