| With the development of science and technology, analytical methods also are developed towards a more convenient direction. Compared with traditional mass spectrometry, ambient mass spectrometry show an advantage that no sample pretreatment during analysis of complex samples. Microwave plasma torch(MPT), as one of the ambient ionization technique, obtain the mass spectra of analyte directly, without sample preparation. The MPT source can desorb/ionize the analyte rapidly and with high efficiency, without toxic solvent, and is much easier for operation. In this study, the ionization performance and mechanism of MPT ion source and the application of MPT-MS were explored systematically.Based on the homemade MPT-MS, the main contents of this thesis are as follows:1. The primary ions which produced by MPT were confirmed. MPT produced a plasma which owns the combination energy of heat, UV-vis irradiation, electrons and charges. These energy will react with the compositions of air and the primary ions were yielded. The data showed that the primary ions, water radical cations, protonated water, and nitrate, were produced by MPT plasma in atmospheric pressure. Moreover, the ionization mechanism was discussed. There were two steps when the sample was introduced by the MPT inner tube. Firstly, the analyte aerosol was atomized, excited and ionized. Secondly, the ions would react with the primary ion and produced the new ions that were detected by mass spectrometer. When the sample was introduced out of the MPT tube, the MPT worked on these three steps: producing primary ions, desorbing the analyte from the sample and ionizing the analyzer.2. Sample introduction methods for inorganic and organics were explored. The results showed that MPT inner tube sample introduction was applicable for inorganics. The other methods were suitable to analyze organics, for instance N2 assisted sampling and MPT ablation sampling. Ionization characterization of MPT was explored, including the excitation capability of MPT plasma, MPT-MSn of different concentrations of metal aqueous, energy distribution of MPT in the air. The results showed that ppb level metal(M) salt solution showed the signal of Mn+. The ppm level metal(M) salt solution obtained M(NO3)a(H2O)b(a-1)+. The position closed to the MPT plasma tail had a highest energy. The study on ionization characterization of MPT provides a basis for applications of MPT-MS.3. MPT-MS was applied to analyze inorganics, organic molecules and proteins. The results show that MPT-MS is able to quantitative detection of Na and K elements in mineral water. The organic that were n-butane and n-heptane can be oxidized to be corresponding alcohol, aldehyde, and acid. There was a direct breakage of the particularly strong C=C bond in benzene through ion-molecule reaction in a MPT plasma, in which one carbon atom was replaced by one atomic nitrogen with the formation of pyridine.4. Microwave plasma torch mass spectrometry(MPT-MS) was applied for analysis of construction stones, without any sample pretreatment. All data from artificial and natural stones were analyzed by principal component analysis(PCA) for differentiation artificial stones and natural stones. The results show that the chemical compositions on the surface of stones, even the inner substances were desorped and ionized by MPT ion source in a short period of time. The acquired spectra show a clear distinction among the construction stones resulted from the different chemical compositions. With the application of PCA, natural stones were successfully differentiated from artificial stones. The method was developed with a high analytical speed, high sensitivity, and no sample pretreatment. The data indicate that the direct MPT-MS analysis allows rapid characterization of untreated solid materials such as construction stones at the molecular level and can provide a new analytical method of mass spectrometry. |
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