Thesis--University of California, Berkeley, 1959. / Includes bibliographical references (p. 71-75).

Thesis (Ph. D.)--University of Rhode Island, 2004. / Typescript. Includes bibliographical references (leaves 138-141).

Thesis (M.Sc.) - University of Queensland, 2005. / Includes bibliography.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 126-137).

Thesis (Ph. D.)--Drexel University, 2006. / Includes abstract and vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 145-150).

The development of new analytical techniques is one of the driving forces in the advancement of scientific understanding. The measurement of the properties of aerosol particles is an active area of research due to the impact aerosol has on atmospheric processes. Single particle size and composition are key properties that govern many atmospheric processes, but the measurement of these properties is challenging due to the large dynamic range of size and composition that exists in the environment. Mineral dust represents a significant fraction of the global aerosol mass loading and has a profound impact on the earth's radiative budget through the direct interaction with solar and terrestrial radiation, and by affecting microphysical properties of clouds. In addition, mineral dust is involved in the geochemical cycling of many compounds that are vital for the health and vitality of ecosystems. The importance of the chemical and crystallographic properties of a material, or mineral phase, has been highlighted recently. Measurements of the elemental composition of single particles is possible with off-line analysis of dust collected on filters , but mineral phase is usually obtained from X-ray diffraction of bulk samples. These techniques are labour intensive and the lack of ambient measurements is a limiting factor in the development of models that attempt to resolve the complexity of atmospheric processes. Time-of-flight mass spectrometry (TOF-MS) is well suited to on-line single particle composition measurements due its sensitivity and high temporal resolution. Single particle mass spectrometry (SPMS) is a class of TOF-MS technique that is able to identify mineral dust particles from their chemical signature in the mass spectrum. Analysis of refractory mineral dust by mass spectrometry requires laser desorption ionisation (LDI) by high energy pulsed lasers, a process that renders the composition measurement non-quantitative due to incomplete ionisation and matrix effects. Consequently, the identification of mineral phase is not possible because the reproducibility of the measurement is lower than the natural variation between common minerals. This thesis reports the development of a commercially available single particle mass spectrometer for the measurement of the physiochemical properties of mineral dust. The optical particle detection system is improved for the more efficient detection of single particles in the size range relevant to the ambient measurement of mineral dust aerosol, and a model is developed that will aid the further development of particle detection in SPMS. A novel method for the on-line differentiation of mineral phase in single particles is presented which exploits differences in ion arrival times at the TOF-MS detector of a silicate molecular ion species, that arise from the influence of mineral phase on the ion formation process during the LDI process. The efficacy of the technique is demonstrated with the differentiation of mineral phase in laboratory generated mineral dust from clay mineral standards. The deployment of the improved instrument to measure Saharan dust outflow resulted in the first ever on-line identification of the clay mineral fraction in ambient mineral dust.

Thin-layer chromatography (TLC) is of great importance for the pharmaceutical industry as a simple, quick, and low cost analytical method. Considerable effort has been made over the past decades to combine the simplicity of TLC with the selectivity and sensitivity of mass spectrometry (MS) detection. In the pharmaceutical industry sensitivity is an especially important factor, since the allowed impurity level of most drugs is under 0.1%.The aim of the present thesis was to develop methods for the direct examination of pharmaceutical compounds from TLC plates by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI TOF MS). The study was started by comparing several approaches for the application of the matrix for direct TLC-MALDI including a newly developed electrospray matrix deposition method. This new method was found to be superior to the other techniques studied. It produced a stable signal, minimised analyte spreading, and hence allowed the scanning of a TLC plate to obtain chromatographic as well as mass spectral data. The plotted mass chromatograms assisted in spot location, and allowed the calculation of Rf-values. These showed good agreement with the Rf -values determined by UV detection. The decrease in mass resolution and mass accuracy commonly observed in TLC-MALDI TOF MS due to the uneven nature of the silica gel layer was corrected by internal recalibration on selected matrix ions during the scanning of the TLC plate. To enhance the signals recorded directly from a TLC plate the use of an extraction solvent prior the matrix application was explored. Further improvements in sensitivity were obtained by modifying a robotic x-y-z axis motion system to act as an electrospray deposition device and by use of special Si 60 F[254] HPTLC-MALDI targets. Using both approaches sensitivities in the high fmol range were obtained. To minimise matrix interference, which can suppress analyte signals, the application of suspensions of particles of different materials and sizes (Co-UFP, TiN, TiO[2], graphite and silicon) onto eluted TLC plates were investigated. The structural analysis of pharmaceutical compounds was achieved by post-source decay - matrix-assisted laser desorption/ionisation (PSD-MALDI) mass spectrometry performed directly on the separated spots. TLC-MALDI MS is not only applicable to the qualitative analysis of pharmaceutical compounds. The generation of quantitative data by using a structural analogue as an internal standard is also described. Different approaches to the incorporation of the internal standard into the TLC plate were tested. The most successful approach was to develop the TLC plate in the mobile phase to which the internal standard was added. Good accuracy, precision, linearity and sensitivity was obtained using this approach.

The motivation of this dissertation is to provide insight towards primary ionization mechanisms within MALDI mass spectrometry. Albeit MALDI-MS is an extensively used analytical technique, the mechanism in which primary ions are created is still under scrutiny. Two current models of primary ionization exist which claim to elucidate the ion formation mechanisms within MALDI. In this work, excited state dynamics of MALDI matrices are shown to play an important role in the ionization mechanism. Upon inspection of the thermodynamic properties of commonly used MALDI matrices, no correlation was observed when plotted against their respective analyte ion yields. However, the excited state singlet lifetimes of these matrices seem to correlate well with their respective analyte ion yields. In the broadest sense, this correlation further supports the fact that photophysical properties of the matrix should be included in current UV-MALDI models. Investigation of a claim which stated singlet energy pooling reactions were absent in the MALDI matrix 2,4,6-trihydroxyacetophenone (THAP) resulted in the discovery of a new energy pooling mechanisms. Characteristic of aromatic ketones such as THAP, intersystem crossing is an efficient process in solution, which gives way to fluorescence in the solid state. Triplet pooling mechanisms from two neighboring THAP molecules are proposed and appear to be dependent on the preparation solvent used. These triplet pooling reactions are thought to play an important role in the primary ion formation mechanism within MALDI. To further investigate the theory of triplet species playing a vital role in MALDI ionization, the internal heavy-atom effect was employed to determine the effect of the triplet species. MALDI mass spectra and excited state decays of these heavy-atom substituted matrices were collected to demonstrate the relationship between triplet species and analyte ionization efficiency. Gas-phase thermodynamics and absorption at 337 nm were also examined to determine if these properties affected the analyte ion signal observed in the MALDI mass spectrum. Using the information collected from the previous study, an advanced MALDI matrix is synthesized. Addition of covalently bound iodine to the gold standard matrix, α-cyano-hydroxycinnamic acid, should drastically improve the performance of the non-substituted matrix due to the increase in triplet species present for pooling reactions. Sample preparation methods in MALDI are examined as are the effects of crystal morphology on the overall signal observed in the mass spectrum. Exciton hopping and pooling rates are highly dependent on intermolecular interactions, so it is expected that crystal packing will affect MALDI. As noted for THAP, preparation solvent plays a significant role in not only crystal morphology, but also the excited state dynamics for all matrices studied.