Study On Detection And Degradation Law Of Common Pesticides Based On Online HS-SPME

Pesticides are widely used in agricultural production of pest control compounds,but in the actual application process,only a small part of the achieved the ideal effect of pest control,the rest of the spraying pesticides are mostly dispersed to a variety of environmental substrates,the most common water and soil.China is a large country in the production and use of pesticides,and its annual average use ranks among the highest in the world.The availability of pesticides has led many criminals to commit poisoning crimes with pesticides.For example,in recent years,there have been frequent cases of poisoning in fish ponds all over the country,which have caused a large area of water pollution and caused a lot of national economic losses,which has attracted great attention from public security organs.Realizing the rapid and efficient analysis of pesticides in environmental matrix and biological samples is not only the requirement of production and life,but also an essential part of cracking down on criminal offences.Therefore,based on the public security actual combat and forensic science poison analysis,this paper used fully automatic online headspace solid-phase microextraction technology combined with gas chromatography-mass spectrometry technology to test 50 kinds of common pesticides in production and life,and used this method to explore the degradation kinetics characteristics of common pesticides at different substrates and temperatures,providing efficient and convenient new ideas for public security organs to handle pesticide poisoning cases,and providing a more comprehensive and specific basis for judicial identification of related cases(events).The results were as follows:1.An automatic online headspace solid phase microextraction gas chromatography mass spectrometry(HS-SPME-GC/MS)method was established for the detection of 50 pesticide residues.In the experiment,2.0 m L test material was salted to saturation and pretreated with HS-SPME.Before extraction,incubation and shaking were performed for 10 min at a shaking rate of250 r/min.The extraction temperature was 60℃and the extraction time was 45 min,the DB-5ms(30 m×0.25 mm×0.25μm)capillary column was selected,and the carrier gas was high purity helium gas.The sample was injected without diverging,and the temperature of the injector was 260℃.The extraction needle was analyzed at the injector for 3 min,and two modes of full scan(SCAN)and selective ion detection(SIM)were used for mass spectrometry.The 50 target pesticides had good linear relationships within their respective linear ranges,and the coefficients of determination(R~2)were all greater than 0.9950.The limits of detection(LOD)and quantitation(LOQ)were 0.25-10.0 ng/m L and 0.5-50.0 ng/m L,and the recoveries were 75.0%-118.0%.The relative standard deviations(RSD)were all less than 18.0%,and the sensitivity met the requirements of public security cases.2.For blood samples,liquid-liquid extraction(LLE)and automatic online HS-SPME combined with GC/MS for the detection of 50 pesticide residues in blood were studied and compared.The recoveries of 50 pesticides treated with LLE were 65.0%-87.0%,and the detection limits were 50.0-1000.0 ng/m L.The recoveries of 50 kinds of pesticides were 75.0%-108.0%and the detection limits were 10.0-100.0 ng/m L.It can be seen that the HS-SPME pretreatment method has obvious sensitivity advantage without using organic extractant,and it has simple operation and high recovery.The relative standard deviation(RSD)of the two pretreatment methods was less than 18.0%.3.Automatic online HS-SPME-GC/MS degradation curves of common pesticides in cases were established.In this study,two environmental substrates of soil and water and two biological substrates of blood and urine were respectively investigated and studied under three temperature conditions of normal temperature(20℃),cold storage(4℃)and freezing(-20℃),in order to provide reference for the inspection period and storage conditions of pesticide materials in practical police operation.The results showed that the degradation characteristics of target pesticides in the four substrates were similar.The degradation rate of pesticide was fast in the initial stage of the experiment,but slowed down gradually with the passage of the experiment time.The degradation process was consistent with the first-order kinetic model,and the equation fitting effect was good.The coefficients of determination(R~2)were 0.82-0.99 in soil,0.79-0.97in water,0.72-0.95 in blood,and 0.75-0.98 in urine.The half-life of different kinds of pesticides was significantly different,and the degradation rate was also significantly different under different temperature conditions and culture substrate conditions.4.The feasibility of the automatic online HS-SPME-GC/MS method established in this paper was verified through the testing and analysis of pesticide poisoning and poisoning cases.At the same time,the nature and time of actual cases were deduced by the degradation curve and dynamic equation of common pesticides established in this paper.