Residue Of Cymoxanil And Oxine-copper In Cucumber

Cucumber is a universal and valuable vegetable which is rich in vitamins. Cymoxanil is often used in cucumber, grapes, potatoes, etc to control downy mildew. Oxine-copper has good preventive and therapeutic effects on fungal and viruses. They can control the downy mildew in cucumber effectively and reduce the economic losses caused by downy mildew. In order to study the residual characteristic and the residuse after soaking in cucumber, the dynamic and final residues of cymoxanil and oxine-copper in cucumber were carried in Shandong Province, Anhui Province, Hebei Province in2012and2013. The residues of cymoxanil and oxine-copper in cucumber and soil were determined by HPLC. The main idea and conclusion of the thesis include to the next means:First of all, a quantitative analysis method was developed for the determination of cymoxanil and oxine-copper residue in cucumber and soil. Cymoxanil and oxine-copper in cucumber were extracted with acetonitrile. Cymoxanil in soil was extracted with acetonitrile and water. Oxine-copper in soil was extracted with acetonitrile and adjusting pH by Sodium hydroxide, and then analyzed by HPLC. Average recoveries of cymoxanil from cucumber and soil samples at levels of0.05mg/kg,0.5mg/kg and1.Omg/kg were in the range from95.8%to110.9%and from106.6%to113.7%respectively, with coefficient of variation in the range from3.6%to4.5%and from4.2%to7.8%respectively. Average recoveries of oxine-copper from cucumber and soil samples at levels of0.05mg/kg (0.05mg/kg in soil),0.5mg/kg and1.0mg/kg were in the range from108.3%to110.9%and from100.8%to109.1%respectively, with coefficient of variation in the range from3.9%to5.1%, from3.3%to4.2%.Secondly, the degradation dynamic of cymoxanil and oxine-copper in cucumber followed the first-degree reaction pattern. The decline half-lives of cymoxanil and oxine-copper in cucumber were from1.8day to2.5day and. from2.6day to4.1day. The decline half-lives of cymoxanil and oxine-copper in cucumber were from3.7day to4.8day and from4.9day to7.4day. Seven days after apraying, there were no cymoxanil residues in cucumber. Fourteen days after apraying, digestion rate of oxine-copper residues was above90%in cucumber.Thirdly, sprayed at3to4times with the application dose of360g a.i./ha and540g a.i./ha, the residues of cymoxanil and oxine-copper in cucumber were from0.0551mg/kg to0.256mg/kg and0.0539mg/kg to～0.563mg/kg. It was suggested that the prehavest interval of cymoxanil and oxine-copper in cucumber was1days. Under field trial conditions, there were positive relation between residue and the amount of spraying.Finally, tap water, hot water, detergent and baking soda were employed to remove cymoxanil and oxine-copper residue with rinseing. The results revealed that imidacloprid residue reduction could be attained to a certain extent, whereas the effectiveness of rinsing with hot water and detergents was not superior to that of rinsing with tap water. Scrubing was a good washing assistant process for reducing the residue of cymoxanil and oxine-copper. The single washing and disinfecting precess could not entirely assure the safety of cucumber. Thus, the combined technologies including two or more processes were suggested to improve the safety of cucumber and postharvest fruits and vegetables.