Studies On The Degradation Dynamics Of Acephate And Its Metabolite Methamidophos In Vegetables

Acephate is degraded into methamidophos during application,which results in higher quality and safety risk.Routine monitoring of agricultural products in Jinhua for years showed that acephate and methamidophos were both detected or exceed the standard limitation sometimes.As the degradation dynamics of acephate and methamidophos in vegetables remain unclear,the effective technical basis is lacked.It is difficult to determine the abnormal application of methamidophos or illegal application of acephate,which brought great difficulties of supervision.In present,the detection of acephate and methamidophos by gas chromatography(GC)of matrix effect is obvious.Meanwhile,there are many problems of wide peak tailing and inlet adsorption chromatography,high detection limit and low accuracy.In this study,through improving methods of pretreatment and optimization of GC conditions,the blank matrix standard solution and standard solution before and after the average calibration method,improving peak shape,eliminating the matrix effect,the detection sensitivity and accuracy was improved.Through investigating the degradation of acephate and its metabolite methamidophos on vegetables,the changes in the degradation process of acephate and methamidophos and the pesticide safety interval were obtained,which provided technical supports for the guidance of agricultural production,agricultural product quality safety supervision and law enforcement.1.Optimization of test methods for residues of acephate and methamidophosBy using blank vegetable matrix containing acephate and methamidophos ingredients to prepare standard solution,standard method for quantitative analysis of GC,the enhancement effects of 2 pesticides were significantly eliminated,and the detection accuracy was improved.Based on the improvement and optimization of the nitrogen condensation temperature,GC inlet conditions and temperature program,etc.,the peak tailing,too wide of the peak width and other issues of acephate and methamidophos chromatographic were significantly improved,the detection sensitivity and precision were improved.Through optimization as above,an inspection method for residues of acephate and methamidophos,the detection accuracy,and sensitivity and precision were significantly improved.The detection limit of the method,recovery rate and relative standard deviation reached 0.007?0.01 mg/L,83.9%?102.5%and 2.4%?4.3%,respectively.2.Degradation law of acephate EC and methamidophos in fieldsVegetables such as cabbage,asparagus and green vegetables were used as the test object.Acephate EC was sprayed in accordance with the existing recommended concentration.Sample and detection were conducted after 0,1,3,5,7,14,28 days spraying to detect acephate and methamidophos residues.The degradation dynamics and their degradation patterns of these 2 pesticides and in vegetables were analyzed as well.The results show that the degradation ratios of acephate and methamidophos in vegetables was 4.7:1?16.2:1,which provided the relationship between the 2 kinds of pesticides in the degradation process of change.The results suggested that there is no illegal drugs if the residue levels of acephate and methamidophos in vegetables is in the range of 4.7:1?16.2:1,that there is illegal drugs if the residue levels of acephate and methamidophos in vegetables exceed the range,which provided the necessary technical reference for the quality and safety inspection and supervision of agricultural products.3.Application procedures and risk assessment of acephateThrough the research on the degradation law of acephate EC on vegetables in the field,the safety intervals of acephate of different vegetables were obtained.The present safety intervals of acephate EC is only determined according to acephate residues.Considering there are some security risks of metabolite methamidophos,this study first proposed the final residues of both 2 kinds of components,which will be used to determine the safety interval of acephate,establish the safe and efficient application procedure of acephate to solve the technical problems caused by the application of acephate and methamidophos exceeding the standardIn summary,there is now still a certain application of acephate in Jinhua,and the detection rate showed a rising trend.Whether during storage,application and process acephate could be degraded into methamidophos,the high toxic pesticide.Therefore,it is necessary to reduce the quality and safety risk from two aspects of controlling the storage environment and regulating the application of the pesticides.The best storage environment of acephate is under 30? and avoiding direct sunlight.Meanwhile,the application of acephate should abide by strictly the standard use,do not raise the applied concentration arbitrarily.The safety interval must be controlled within 7 days or more under field cultivation.The safety interval could be extended at least 7 days.