Study On Residue And Environmental Behavior Of 2,4-D Isooctyl Ester

2,4-D isooctyl ester is a phenoxycarboxylic ester and selective contact herbicide,which is mainly used to control broad-leaved weeds in gramineous crops such as maize et.al.2,4-D isooctyl ester has the characteristics of low volatility,high boiling point,not easy to drift,relatively safe and so on.It has gradually come into our sight and is widely used.Although2,4-D isooctyl ester plays an important role in agricultural production,it has low toxicity and risks to human,animal,microorganism and environment.Studying the residue analysis and environmental degradation behavior of 2,4-D isooctyl ester is of great significance for reducing its risk and providing theoretical guidance with certain practical significance for its rational application in agricultural production.In this paper,the residue detection methods of 2,4-D isooctyl ester and its degradation product 2,4-D were studied.A Qu ECh ERS-gas chromatography(Qu ECh ERS-GC-ECD)method was established for the determination of 2,4-D isooctyl ester residues in soil,maize and maize plants.The samples were extracted by acetone,purified by GCB,PSA and C18,separated by HP-5 capillary column,temperature programmed,and quantified by matrix matching standard solution external standard method,and qualitative and quantitative analysis by gas chromatography.Qu ECh ERS-HPLC-MS/MS was established to detect the residues of2,4-D in soil,maize and maize plants.The samples were extracted with 0.5% acetonitrile formate solution.GCB and C18 were used as adsorption materials for Qu ECh ERS.Matrix matching standard solution external standard method was used for quantitative analysis,and qualitative and quantitative analysis was carried out by HPLC-MS/MS.It was met the requirements of the test that accuracy,sensitivity and precision of the method.Secondly,the storage stability of 2,4-D isooctyl ester and its degradation product 2,4-D in maize and green maize at-20 ℃ was studied.Within six months,the recoveries of 2,4-D isooctyl ester and 2,4-D in maize and green maize met the requirements of pesticide residue test criteria.The degradation rates of 2,4-D isooctyl ester and 2,4-D in maize and green maize were less than 30%,indicating that the storage was stable.Therefore,in the process of residuetest of 2,4-D isooctyl ester,the sample should be frozen at-20℃ and completed within 6months to ensure the accuracy of test data.Then,the residues and degradation dynamics of 2,4-D isooctyl ester in maize field were studied through field experiments in 2017 and 2018.Our country stipulates that the residue of2,4-D isooctyl ester is the sum of 2,4-D isooctyl ester and 2,4-D.The results were as follows:In Liaoning and Anhui experimental sites,the half-lives of 2,4-D isooctyl ester in maize plants were 8.77 and 9.63 days respectively;the half-lives in soil were 12.83 and 16.50 days respectively,which belonged to degradable pesticides(t1/2≤30 d).The residues of 2,4-D isooctyl ester residues in maize plants,maize grains and soil collected at 7 experimental sites in Liaoning,Anhui,Beijing,Shanxi,Hunan,Guizhou and Heilongjiang during harvest period were less than the temporary maximum residue limit of 2,4-D isooctyl ester in maize established in China,which was 0.1 mg/kg.Finally,the hydrolysis and photolysis characteristics of 2,4-D isooctyl ester under different conditions were studied by indoor simulation test.The results showed that the hydrolysis rate of 2,4-D isooctyl ester in acidic and alkaline conditions was faster than that in neutral conditions;the hydrolysis rate of 2,4-D isooctyl ester was obviously accelerated with the increase of temperature;the hydrolysis rate of 2,4-D isooctyl ester in paddy field water and tap water was higher than that in distilled water and river water;the higher the initial concentration,the faster the hydrolysis rate.The photolysis rate of 2,4-D isooctyl ester decreases with the increase of p H value;the photolysis rate of 2,4-D isooctyl ester in different types of water is river water >paddy field water >tap water >distilled water;the photolysis rate of 2,4-D isooctyl ester under different light sources is 500 W mercury lamp > 300 W mercury lamp > 500 W xenon lamp in turn;the higher the initial concentration is,the faster the photolysis rate of 2,4-D isooctyl ester is.The main product of hydrolysis and photolysis of2,4-D isooctyl ester is 2,4-D,and its degradation mechanism is mainly ester hydrolysis.The results can provide theoretical reference for the rational use of 2,4-D isooctyl ester and environmental risk assessment.