Residue Analysis And Digestion Dynamics Study Of 30% Pyraclostrobin Suspension On Cucumber

Cucumber is one of main varieties of vegetables in China, evey year downy mildew causes a great economic loss in the production of cucumber. Pyraclostrobin is widely used in the production of cucumber due to its efficient, low toxicity and abroad fungicidal activity. In order to ensure the edible safety of cucumber, in this work a method was established to determine the residues of pyraclostrobin in cucumber and soil. Through the field trial to study the degradation dynamics and terminal residues of 30% pyraclostrobin suspending concentrate in cucumber and provide reasonable suggestion of it in cucumber.In this work, an ultra performance liquid chromatography with PDA detector(UPLC-PDA) method was established for the residue of pyraclostrobin in soil and cucumber. The QuEChERS method was used for sample pretreatment procedure, after extract with acetonitrile and cleaning up by N-Propylethylenediamine(PSA). LOQs in soil and cucumber were 0.05 mg/kg and 0.02 mg/kg, respectively. The spiked levels of pyraclostrobin in cucumber and soil were 0.05, 0.5, 5.0 mg/kg and 0.02, 0.5, 5.0 mg/kg, respectively. The recoveries were ranged 92.15 to 98.44% with RSDs between 1.07 and 5.42% in soil and cucumber. The accuracy and sensitivity of the method meet the requirements of pesticide residues analysis.The field trials of 30% pyraclostrobin(Suspending concentrate, SC) were performed in Guizhou, Guangxi and Tianjin province during the agricultural season in 2014 and 2015. The results indicated that the degradation of pyraclostrobin is very fast in cucumber. Otherwise, there has on regularity in the degradation of pyraclostrobin in soil?The results of terminal experiment showed that spraying for four time and five times and interval of 7 days at the low dosage and high dosage(180-270 g a.i/ha), in 2014 and 2015, the maximum residue of 30 % pyraclostrobin SC was 3.70-0.43 mg/kg in cucumber and 0.49-0.60 mg/kg in soil at harvest time. Therefore, 30 % pyraclostrobin SC can be applied safely on cucumber with the recommended dosage and time.Meanwhile, this study also invsitgate the factors which effect degradation of pyraclostrobin in soil, the results showed that, the degradation of pyraclostrobin in soil were mainly influenced by organic matter,moisture content and temperature?The half lives of pyraclostrobin in interior simulating experiment was about 80 d and the degradation of pyraclostrobin is very slow in soil. So there may has some adverse influence on environment.