Doctor of Philosophy (PhD)
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used for off-line analysis of bioaerosols. The overall goal of the work is to develop methods and instrumentation to minimize sample treatment and maximize sensitivity and selectivity for bioaerosol analysis. This work is divided into three parts: sample preparation, test bioaerosol analysis, and instrument development. Untreated silicon wafer substrates were used as an alternate to conventional stainless steel targets and proved to be excellent substrates for large molecule analyses as well as small molecule analyses with excellent spot-to-spot and shot-to-shot reproducibility, which is useful for high-throughput and automated sample analysis. MALDI sample preparation was optimized by the L9 (33) orthogonal array of Taguchi’s systematic approach using the effects of various parameters such as matrices, solvents, and deposition methods. Test bioaerosol particles were generated from a nebulized bacterial suspension and were collected onto bare or matrix pre-coated MALDI targets placed in an impactor for off-line analysis. The MALDI matrices or solvents were added on the target afterward by pipette or spraying to obtain signals similar to the dried droplet method. Finally, two novel MALDI mass spectrometers were constructed to test new bioaerosol ionization approaches. A transmission geometry MALDI-MS, in which the laser irradiates samples from back side of the target, enabled a tight laser focusing by coupling a microscope objective lens outside of the vacuum. The instrument is applicable to the analysis of single deposited bioaerosol particles. A UV and IR MALDI ion mobility mass spectrometer was used for the analysis of complex bioaerosol mixtures by two-dimensional separation of ions according to their shapes and masses. The instrument separates the complex bioaerosol mixtures into different classes on trend lines that simplify the analysis. These trend lines include lipids, peptides/proteins, and oligonucleotides.
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Kim, Jae-Kuk, "Off-line MALDI mass spectrometry of bioaerosols" (2008). LSU Doctoral Dissertations. 3374.
Kermit K. Murray