Study On The Degradation Effect And Product Analysis Of Cypermethrin By Chlorine Dioxide Treatment

Cypermethrin is an efficient broad-spectrum insecticide which is stable to light,heat,and also stable in neutral and weakly acidic media.Cypermethrin's long half-live in the environment make it difficult to degrade rapidly.Long-term application will cause accumulation in the environment and agricultural products,resulting in greater safety risks.Therefore,how to reduce the pesticide residue of cypermethrin efficiently and concisely has become a concern for people.Chlorine dioxide is a chlorine atom that binds with two oxygen atoms with two coordination bonds,and unpaired lone pair electrons are present in the outer layer of chlorine atoms.It is a highly efficient and strong oxidant with stability and selectivity.Current research has proven that chlorine dioxide reacts with various substances only in the oxidation reaction and does not generate chloro reaction to generate odors and carcinogens such as trichloromethane,chlorophenol and trihalomethanes..Therefore,the use of chlorine dioxide won't cause secondary pollution to the environment.Studies have shown that chlorine dioxide has a certain degree of degradation of EBDCs,ETU,deltamethrin,methamidophos,butyl-4,6-dinitrophenol(DNBP)and other pesticides,and the degradation effect is up to 100%.And it has been widely used in disinfection and sterilization,bleaching and deodorization,fruit and vegetable preservation,food industry and other fields,but chlorine dioxide on the degradation effect of cypermethrin and it's toxicology studies have not been reported..In this dissertation,the effect of chlorine dioxide on the degradation of cypermethrin was taken as the starting point.Based on the single factor experiment,the degradation conditions of cypermethrin pesticides were optimized by response surface methodology,and the effect of chlorine dioxide on the quality of spinach was studied.These results provide a theoretical basis for further application to actual production.And a gas chromatography-mass spectrometry(GC-MS)was developed to analyze the main degradation products of cypermethrin in chlorine dioxide solution.The main findings are as follows:1.Study on the optimum degradation condition of cypermethrin by chlorine dioxideThe effects of chlorine dioxide on the degradation of cypermethrin were investigated under different temperatures,different reaction times,different concentrations of chlorine dioxide and different pH conditions.Based on single factorexperiments,the degradation conditions of cypermethrin pesticides were optimized by response surface methodology.The experimental results showed that chlorine dioxide has a significant degradation effect on cypermethrin.The optimal reaction conditions were as follows:chlorine dioxide concentration 210 mg/L,temperature 26?,and the maximum degradation rate of cypermethrin was 87.96%when the reaction time was 26 min.The results showed that chlorine dioxide can effectively degrade cypermethrin.2.The effect of chlorine dioxide on the degradation of cypermethrin residues in spinachTo investigate the effect of chlorine dioxide on the degradation of cypermethrin residues in spinach,commercially available 4.5%cypermethrin EC was assigned into the recommended dose,1.5 times the recommended dose,and twice the recommended dose of the liquid according to the effective dosage of the instructions and sprayed onto the spinach separately.By detecting the pesticide residue in infected spinach,it was found that the original residue of cypermethrin was far higher than the national food safety standards.The highest degradation rate was 94.18%when 150mg/L chlorine dioxide solution was used to treat different concentrations of spinach,the highest degradation rate was 96.12%when 210mg/L chlorine dioxide solution was used to treat different concentrations of spinach,which was far higher than the highest degradation rate of 65.10%when chlorine dioxide gas was used to treat different concentrations of spinach.The results showed that chlorine dioxide liquid treatment group's cypermethrin degradation of spinach was better than chlorine dioxide gas treatment group,greatly improving the safety of fruit and vegetable consumption3.Effect of chlorine dioxide rreatment on spinach qualityTo investigate the effect of chlorine dioxide on spinach quality,spinach was treated with different concentrations of chlorine dioxide gas and liquid,stored at 4? and measured for soluble solids content,weight loss rate,nitrate,chlorophyll,peroxidase and ascorbic acid content during storage of spinach.The results showed that the treatment of spinach with 150 mg/L chlorine dioxide liquid could maintain the appearance,texture,and nutrient composition of spinach better than the control spinach,and did not negatively affect the texture of spinach.ClO2 treatment can effectively slow the decrease of soluble solids content,catalase activity and Vc content,and the mitigation efficiency is positively correlated with ClO2 concentration.4.Analysis of the degradation products of cypermethrin treated with chlorine dioxideThe degradation products of cypermethrin treated with chlorine dioxide were detected and analyzed by gas chromatography-mass spectrometry.A total of four major degradation products were obtained,namely C17H34O2(Rt=11.435,m/z=270.256)and C16H22O4(Rt=11.999,m/z=278.152),C10H21N0(Rt=16.182,m/z=171.162),C23H32O2(Rt=18.716,m/z=340.24).In summary,the results of this study indicate that chlorine dioxide can effectively degrade cypermethrin.Under the best degradation conditions,the degradation rate of cypermethrin in solution is as high as 87.96%.Four major degradation products were obtained;150 mg/L was used.The highest degradation rate was 94.18%when 150mg/L chlorine dioxide solution was used to treat cypermethrin in infected spinach,and has no adverse effect on the texture and nutrient content of spinach.