| Chemical warfare agents(CWAs)are chemicals that are toxic to the human body and have military operational value.They have been manufactured into chemical weapons and have been used many times during wars and non-military terrorist activities.Now,terrorist attacks and assassinations related to chemical weapons are posing a huge threaten.For example,the use of nerve agents was detected in the“Assassination of Kim Jong-nam”case and“Poisoning of Sergei and Yulia Skripal”case in recent year,which caused huge social panic and affected international political opinion,and became one of the critical uncertainties that affect world peace.Rapid screening of CWAs and their related chemicals is important to prevention and control of chemical weapons.CWAs and their degradation products,precursors,impurities and other chemicals are important environmental markers for chemical weapons verification.They were listed in the Chemical Weapons Convention(CWC)schedules,43 categories with tens of millions structure possibilities.Due to these chemicals character:countless amounts,traceability requirements,low concentration in complex samples and emerging new structures,which has brought great difficulties and challenges to the screening work.However,the commonly used methods based on GC-MS cannot directly analyze low volatile degradation products,the current analysis methods using LC-MS are selective and target screening methods,which can only identify several or one class of chemicals.It is necessary to achieve sensitive untargeted screening and identification for large number of unknown compounds simultaneously.This thesis aims at establish untargeted screening strategies for different types CWAs related chemicals using LC-MS.Based on the mass fragment behavior of chemicals with different parent nucleus,novel processing methods were developed,“alerting ion”matching method was established to pick up nerve agents related substances,diagnostic ion and neutral loss filtering methods were developed to find out2B.04 simulants and fentanyl analogues.Additionally,retention time prediction model was built to distinguish isomers.These strategies can achieve sensitive screening for massive unknowns,and provide a technical support for the trace forensic verification of CWAs related chemicals in environmental samples.This thesis divided six chapters.In the first chapter,the current development of CWAs was introduced,which include the hazards of CWAs,Control and verification of CWAs and chemicals in Chemical Weapons Convention(CWC)Schedules;And the advantages and disadvantages of screening methods using GC-MS and LC-MS;In addition,the development of novel screening strategies and technical methods using LC-MS was introduced.Finally,the research significance and research innovation of this thesis are proposed.In the second chapter,we summarized nerve agents(NAs)and their degradation products(DPs)with a total of 410,000 structure possibilities according to 1.A.01-1.A.03in the CWC Schedules.A three-step integrated untargeted screening strategy was firstly developed based on a high-resolution mass spectrometry.First,an extensible homemade library for targeted screening of common classical agents was established.Second,a set of in-source collision-induced dissociation MS-Alerting Ions was extracted and concluded based on the fragmentation behavior studies,which included 40 specific alerting ions and 10 types of characteristic structural fragments from total NAs and their DPs.A novel“Alerting Ion”searching method was developed to rapidly and sensitively screen whether or not there were nerve agent-related compounds and which type.Third,we built a theoretical exact mass database including 202 accurate masses or molecular formulas,which could cover all structural possibilities of the NAs and their DPs.Comprehensively,the elemental composition of pseudomolecular ions,fragment ions,MS/MS spectra and isotope pattern information were obtained from the full MS/dd-MS~2experiments and elucidated for identification of the candidates selected in the screening step.This strategy had been successfully applied to the identification of unknown chemicals in real samples with good stability and a low limit of detection of 1-10 ng/m L.These procedures would be applicable for trace forensic investigations in cases of alleged use of nerve agents.In the third chapter,based on the mass fragment pathways of different 2B.04related chemicals,diagnostic ions of each type were choosen to pick up unknown chemicals.Focus on two major types of chemicals alkyl phosphonophates and alkyl phosphonothioates related analogues,16 characteristic diagnostic ions were choose for the screening of two types compounds.An integrated untargeted screening strategy based on diagnostic ion filtering and retention time prediction method was established.First step was to found out the related chemicals through diagnostic ion filtering methods.Then obtained proposed structure using MS and MS/MS fragments analysis.Finally,isomers of structure candidates were distinguished using retention time prediction methods,and confirmed by comparing with reference standards.The method was applied to the screening of OPCW PTs(Proficiency tests)samples.In the fourth chapter,an untargeted screening strategy for mustards and other CWAs besides nerve agents was established.First step was pre-target screening of chemicals rapidly with multiple reaction monitoring(MRM)method at good sensitivity.Next step was post-target screening of unexpected chemicals.An extensible HRMS home-made library was built,which contained not only 57 common classical agents with reference standards but an extensible theoretical mass database including 56chemicals without reference standards.Final step was identification of unknown chemicals,as it was not found in previous procedures.Screening other CWAs related chemicals,which were not included in our home-made library,utilized fragments ions analysis and structure elucidation techniques.In conclusion,unambiguous screening result was summarized and deducted from above three procedures.After validation,this three-step screening strategy has both robust stability and a good limit of detection(LOD).It was also demonstrated that its successful application prospect in identification of spiking chemicals in samples from OPCW PTs.In the fifth chapter,based on the mass fragment pathways of fentanyl compounds with different substituents,structural modification-mass fragment model was constructed to propose mass fragments of new fentanyl analogs.An integrated screening strategy for fentanyl analogues was established.First,data was searched in theoretical mass database,which exceeds 100 reported analogues.Second,extract and classify fentanyl analogues by diagnostic ion filtering(DIF)and neutral loss filtering(NLF)for entire chemical classes including novel derivatives.This strategy was validated successively through some unknown materials and one postmodern analysis that confirmed fentanyl in the blood samples.In the sixth chapter,based on the commercial high-resolution mass spectrometry database,more than 200 common toxicants and medicines(hypertensive drugs,glucocorticoids etc.)were added in the database.A comprehensive screening strategy was established based on database searching method combined with post-target extract related chemicals including hydrolysates and metabolites in the samples.Which has been successfully applied to screening and identifying unknown toxicants in food poisoning patients'vomit and feces,providing efficient screening method for rapid detection and identification of toxicants in unknown poisoning samples. |
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