Detection Of Gaseous Negative Ions And Their Interactions With Compounds Through Mass Spectrometry

Gaseous negative ions can effectively remove haze,degrade indoor organic pollutants and improve human health,which has a broad application prospect.However,the gaseous negative ions which play an important role in the process have been unknown to us.A near-real-time detection method is sought for the analysis of gaseous negative ions.Mass spectrometry,with high specificity,sensitivity and online detection,becomes a powerful tool for the identification of gaseous negative ions according to the obtained mass to charge ratio.In this thesis,an ambient mass spectrometry is applied to this research.The contents were summarized as follows:1.We established a tube flow based atmospheric pressure corona discharge mass spectrometry system,providing a convenient platform for a near-real-time detection of gaseous negative ions generated in specific gas.Ions species produced in oxygen,synthetic air,nitrogen and argon atmosphere were investigated,and secondary mass spectrometry detection was utilized for further identification of these ions.Allowing for the sensibility of corona discharge within various external environments,vital factors including the tip voltage and gas flow rate were investigated to assess their influences on the generation of gaseous negative ions.It contributed to understanding of formation mechanism in corona discharge based on the detected ions.Besides,the produced negative ions could be used for subsequent experiments.2.The evolution of negative air ions and relevant degrading performance on indoor organic contaminants like aldehydes,benzene homologues and esters were investigated in this work.Negative air ions composed of a single ion species CO3-could be produced in T-shaped tube with atmosphere pressure corona discharge ionization in synthetic air(21% O2+79% N2),which displayed excellent stability,reproducibility and intensity.Combining gaseous ions with IOCs spray provided a convenient platform for study of chemical properties of negative air ions and interactions with IOCs.Relevant intermediate products could be detected during combination process,which helped us to conclude principles according to different reactants.Besides,negative air ions could be applied to the tentative clearance of aldehydes,benzene homologues and esters.It was also believed that this strategy could be extended to the ionization of substance which was difficult for traditional ESI source.This platform proved to be an efficient method for analysis of the interactions between specific negative ions and various chemical compounds.In conclusion,we have successfully developed several novel methods for analysis of gaseous negative ions through mass spectrometry.These innovative ideas have been applied to a near-real-time detection of gaseous negative ions generated in specific gas and their interactions with organic compounds through mass spectrometry.We believe that our developed platform will be of great significance in the basic and applied research in gaseous negative ions.