Testing Of Photoionization/Orthogonal Acceleration Time-of-flight Mass Spectrometry And Development Of Reflectible VUV Ionization Source

The dissertation mainly includes two parts:the testing of the photoionization orthogonal acceleration time-of-flight mass spectrometry and the design of a reflectible vacuum ultraviolet photoionization source. Firstly, photoionization in combination withorthogonal acceleration time-of-flight mass spectrometry system was tested,simple and complex samples were studied. Secondly, on the basis of previous work, a reflectible vacuum ultraviolet ionization source was developed.The dissertation is divided into three chapters. The first chapter summarizes the research status of mass spectrometry method, the structures of mass spectrometry, and principles were introduced. In the structure part, the types and principles of ion source and mass analyzer were introduced. Finally, the mass spectrometer’s main performance parameters such as resolution, sensitivity, mass range, precision and accuracy were briefly addressed.In the second chapter, the buildingand testing process of photoionization orthogonal acceleration time-of-flight mass spectrometry are described. Parameters such as thelength of the capillary, the pressure in the ionization chamber, voltages of thefocusing and repelling electrodes are optimized. In addition, several common ion guide devices such as capillary, electrostatic lens are described, and the voltages applied on the einzel lens used in the experiment were optimized by SIMION simulation and experiments. Then the optimal parameters of the time-of-flight mass spectrometry were given. After finishing the testing procedures, simple samples such as acetone, toluene and complex sample such as the gaseous composition of mainstream cigarette smoke was analyzed to testthe instrument built.On the basis of previous research work, a reflectible vacuum ultraviolet ionization source was designed. By means of thermal evaporation, opposite surfaces of the DFE and DCE were aluminized, and acetone, toluene,1,3-butadiene were analyzed in the experiments. The results show that the ionization source can effectively increase the vacuum ultraviolet light path, enhance the sample ionization efficiency, and thus improve the sensitivity of the instrument. The performance of this novel ionization sourcecan befurther improvedby using a radio frequency power supply on the VUV lamp, reducing the hole size of the repelling plate.