| Mass spectrometry is a versatile and indispensable tool in scientific research.Since the advent of the mass spectrometry in the early 20th century,it has gradually developed into multidisciplinary technology,which involves in many research fields of science.The study on ion source,which creates atomic and molecular ions,has always been a hot research topic in mass spectrometry.The desorption electrospray ionization(DESI),firstly introduced in 2004,opened up a new door to ionization technology.Following the introduction of DESI.a large number of ambient ionization sources have been developed.However,most of these technologies focus on the detection of solid and liquid samples,and there are fewer ambient ionization techniques specifically designed for gas detection.Based on the previous study of our group,we further discussed the sampling method of mass spectrometry for gas detection.By modifying the existing sampling setup,we made the effort to improve the limit of detection and sensitivity of the method.Localization of gas source is a very important issue in gas detection.By using the existing sampling setup,we made the effort to apply our setup to localize the gas source.Besides that,we also monitored the diffusion of smoke with our improved setup.For the research topic of gas spatial resolution,we combined the newly designed sampling device with a program-controlled X-Y-Z moving stage,which enables our setup to image gas diffusion in three-dimensional space.The main content of this paper can be summarized as follows:Chapter 1:The chapter gives a brief review of the history of mass spectrometer development and the main components of mass spectrometry.The ion source,which is a key device for ion generation is described in detail.Besides that,a brief introduction to the synthesis technology of fullerenes is discussed.Chapter 2:Based on the previous research of our group,we further studied the detection of gaseous compounds by mass spectrometry.Firstly,we improved the sensitivity of the original method by using liquid nitrogen cryogenic enrichment,which is useful for enriching the compound with a large total amount but a low relatively amount in the environment by extending the sampling time.Secondly,we designed a device to acquire the limit of detection of four representative compounds.Chapter 3:Based on setup described in previous chapter,we conducted a serious of experiments on gas source localization.We applied our method to locate single gas source and two gas sources.Besides that,we use our setup to monitor the dynamic diffusion of cigarette smoke.Inspired by these works,we used the modified setup to distinguish two adjacent gas sources.Meanwhile,we combined the similar modified setup with a program-controlled moving stage to test gaseous samples in a high-throughput manner.Chapter 4:Mass spectrometry imaging is a technique used to visualize the spatial distribution of molecules,which has been a hotspot in mass spectrometry study over the past twenty years.However,this technique has never been used to visualize the otherwise transparent gaseous compounds.Gases are intangible in three-dimensional space,and their diffusion changes over time.There have been some techniques using optical imaging principles to instantaneously visualize a gas by taking a spectral image of a particular gaseous compound.Nevertheless,these methods are only capable of detecting a specific target compound,which means scarcely capable of detecting unknown compounds.Mass spectrometry imaging usually costs a long time to acquire data and is difficult to characterize the dynamic diffusion of gaseous compounds.Our newly designed sampling setup analyzes samples by continuously aspirating gaseous compounds in a controllable negative pressure utilizing the Venturi effect of the nebulizer.Combining the sampling tubing with a program-controlled X-Y-Z platform,therefore,enables sniffing-MS to image stable 3-D gas diffusion.Chapter 5:This chapter summarizes the main content of the dissertation and gives a prospect of the future work. |
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