Development of mass spectrometry methodology and instrumentation for analysis of complex mixtures
Mass spectrometry is a powerful tool for the analysis of complex mixtures. It provides precise measurements of mass and elemental composition of analytes as well as structural elucidation of unknown analytes without prior separation. Tandem mass spectrometry (MSn) is often the technique of choice for structural elucidation of unknown analytes. The coupling of mass spectrometry with high performance liquid chromatography (HPLC) to enable front end separation of complex mixtures has allowed for trace level analysis of components in complex mixtures. Ionization is a critical step in mass spectrometry. The ionization technique used for a given sample determines the suitability of the methodology to a given analyte. An ionization technique suited for mixture analysis should form one ion type per analyte without fragmentation to retain molecular weight information. Common MSn techniques include collision-activated dissociation (CAD) and ion-molecule reactions. This thesis focuses on the development of mass spectrometry methodologies and instrumentation to enable optimal ionization and analysis of complex mixtures of biofuel, pharmaceutical, peptide, and petroleum samples. Chemical ionization via the use of μ-chloromanganese dimer, ClMn2+, was explored for the ionization of polar and non-polar hydrocarbons. Electron ionization was investigated as a method for the ionization and simultaneous fragmentation of peptides desorbed using laser-induced acoustic desorption (LIAD). CAD was used to elucidate the structures of the molecular ions of asphaltene model compounds produced via atmospheric pressure chemical ionization using carbon disulfide as a chemical ionization reagent. Further, CAD was used to explore fragmentation patterns of deprotonated lignin related analytes found in degraded biomass samples. Lignin analytes were deprotonated using electrospray ionization doped with sodium hydroxide. Ion-molecule reactions were used to elucidate the structures of deprotonated lignin model compounds and degraded mixtures, small monofunctional analytes produced via electrospray ionization. Finally, a pulsed valve sample introduction interface was designed to enable rapid screening of multiple functional group selective ion-molecule reactions in a linear quadruple ion trap.
Kenttamaa, Purdue University.
Analytical chemistry|Inorganic chemistry
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