Advancements in coupling ambient plasma ionization and drift tube ion mobility spectrometry with mass spectrometry
Keelor, Joel D.
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This body of work describes progress in the development of ambient ionization and ion mobility separation technologies coupled at the atmospheric pressure interface of modern mass spectrometers. The physiochemical forces governing ambient plasma-based ion source efficiency were thoroughly evaluated, with studies involving a visual survey of plasma source fluid dynamics to inform optimal sampling practice, as well as a spectroscopic investigation to determine the abundance of limiting excited-state reagents generated in different types of helium plasma discharges. A versatile new hybrid ion source design was inspired based on these plasma source characterization studies, featuring interchangeable configurations for vacuum-enhanced sample introduction via laser desorption or transmission mode geometry, improving overall sampling efficiency. Another new ion source scheme which made use of a repeller-point electrode was also devised, overcoming the challenges of direct sampling for an ambient glow discharge source paired with a standalone drift tube ion mobility detector. Additionally, a miniaturized microplasma device intended for portability and low-resource operation in remote environmental monitoring applications is reported. The final research efforts were directed toward development of a new high-resolution multidimensional ion mobility-mass spectrometry platform, where an accurate-mass Fourier Transform ion trap mass spectrometer was equipped with an atmospheric pressure drift tube ion mobility spectrometer. System performance was diagnosed for the different dual-gate mobility operations and mass analyzer scan cycle parameters, showcasing promising applications and future method modifications to improve instrument capabilities.