Type of Document Dissertation Author Schaub, Tanner M URN etd-11092004-193233 Title Field Desorption Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Degree Doctor of Philosophy Department Chemistry and Biochemistry, Department of Advisory Committee
Advisor Name Title Alan Marshall Committee Chair Christopher Hendrickson Committee Co-Chair Naresh Dalal Committee Member Vincent Salters Committee Member William Cooper Committee Member Keywords
- Mass Spectrometry
- Complex Mixture
- High Resolution
- Field Ionization
- Field Desorption
Date of Defense 2003-11-03 Availability unrestricted AbstractThis, the 30th year of Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS),1 has marked a milestone for incredible growth in the field of high-resolution mass spectrometry. The most notable realizations of this fact being the successful installation of the highest field FT-ICR MS system assembled to date (14.5 Tesla) and the recent release of the most advanced commercial FT-ICR MS system by the world’s largest instrument manufacturer. The 14.5 T instrument, housed at the national FT-ICR user facility at the National High Magnetic Field Laboratory in Tallahassee Florida, will undoubtedly set new records for a number of the most important figures of merit in mass spectrometry in the coming months. The sale of approximately 75 commercial FT-MS systems this year brings the total number of these instruments to 500+ worldwide – more than double the number of operating FT-ICR systems worldwide only six years ago.
The prime reasons for the wide utility and application of FT-ICR MS are the unmatched mass resolving power and mass accuracy that are feasible with the technique. Factors that contribute to the high resolving power and mass accuracy of FT-ICR include: ion observation duration much longer than for other mass spectrometers, the measurement of frequency (which is one of the most accurately measured experimental parameters), use of high field, spatially homogeneous superconducting magnets, reliable frequency to m/z conversion, and the independence of cyclotron frequency from ion kinetic energy. Those attributes, combined with protracted ion storage duration, ion reaction chemistry capability, multistage MSn experiments and interface to a variety of ionization sources have made modern FT-ICR a unique tool for analytical experiments - experiments that range from environmental and petrochemical analyses to forensic analysis and to biological and pharmaceutical applications. The history and theory of FT-ICR MS are presented in Chapter 1 along with a discussion of petroleum analysis by FT-ICR MS.
The recent development of FT-ICR MS methods for petrochemical analysis has been led by the FT-ICR group at the National High Magnetic Field Laboratory. While that development has primarily focused on the polar constitution of petrochemicals through the use of high field electrospray ionization (ESI) FT-ICR MS, efforts to expand the number of observable chemical classes (especially to nonpolar species) have been made. For example, an internal electron ionization (EI) FT-ICR mass spectrometer has been demonstrated for analysis of volatile and semi-volatile light end petrochemical samples (e.g. diesel fuels) and recently a 7T external electron ionization instrument has been developed for similar samples.
Field desorption ionization (FD) provides a means to access nonvolatile nonpolar petrochemical constituents from heavy petroleum. The development of field desorption ionization FT-ICR mass spectrometry for nonpolar petrochemical analysis began with a proof of concept achieved by the successful interface of a commercial field desorption source with our 9.4 T FT-ICR instrument, which is typically configured for electrospray ionization. The results of that experiment are the subject of Chapter 2.
To further identify the value of high-resolution FD FT-ICR MS we have built a complete actively-shielded 9.4 T FD FT-ICR mass spectrometer that is now available daily at the NSF High-Field FT-ICR MS Facility of the National High Magnetic Field Laboratory. Design details and operation methodology for this instrument are discussed in Chapter 3. That report includes a model compound study and emitter degradation scanning electron microscopy survey that provide the basis for interpretation of an example broadband FD FT-ICR crude oil mass spectrum.
Field desorption ionization MS is typically a pulsed ionization technique, where ions are produced transiently and analyzed, after which sample is reapplied. Operation of the ion source in this manner inhibits the ability to sum a large (>20) number of petroleum mass spectra (as is useful and common for our ESI FT-ICR petrochemical analyses). In order to ensemble average, we have developed a novel FD sample introduction technique, termed continuous flow field desorption (CF FD), which converts the pulsed FD ion source to a continuous ion generator. The continuous flow FD technique is detailed in Chapter 4.
In Chapter 5, we apply continuous flow FD FT-ICR to the analysis of four aromatic fractions from ExxonMobil refinery process streams. Continuous flow sample introduction allowed summation of 75 time domain signals for each of these samples and yielded spectra with extremely high mass accuracy at high mass resolving power. From the elemental composition assignments, we discuss heteroatom distribution, degree of unsaturation, and carbon number distribution for numerous observed chemical classes and types. This analysis provides insight into the specificity of the refinery operations.
As is common at a user facility, application of the FD FT-ICR mass spectrometer has involved collaboration with numerous external research groups including those from ExxonMobil Research and Engineering, NewFields Environmental Forensics Practice, the Vienna Institute of Technology, the National Oceanographic and Atmospheric Administration (NOAA), and the University of Birmingham in England. It is often difficult to predict the outcome of such ventures and while each of the first five chapters include published (or submitted) data, Chapter 6 includes an account of two unpublished external user projects for which FD FT-ICR MS was successfully performed within our laboratory. Those projects are FD FT-ICR MS characterization of natural hydrocarbon input to the northern Gulf of Alaska (with NOAA) and analysis of coal-tars subjected to various thermal treatments (with NewFields). Here, we use that data as the basis for discussion of obstacles, shortcomings, and future directions for the application of FD FT-ICR MS technology and to provide a complete account of the FD FT-ICR MS research projects performed to date.
Filename Size Approximate Download Time (Hours:Minutes:Seconds)
28.8 Modem 56K Modem ISDN (64 Kb) ISDN (128 Kb) Higher-speed Access Schaub_Dissertation.pdf 3.29 Mb 00:15:12 00:07:49 00:06:50 00:03:25 00:00:17