Part of the work described in this dissertation has involved development of instrumentation for the analysis of aerosol compounds. A quadrupole ion trap mass spectrometer (QITMS) is modified to sample particles via an aerodynamic lens inlet. The instrument has a unique capability for volatilization and chemical ionization within the heated ion trap that reduces fragmentation compared to other methods. Compounds in particles are detected in real time at low concentrations, over a broad concentration range, and in complex mixtures. Unlike most mass spectrometry systems used for aerosol detection, the aerosol QITMS is able to perform tandem mass spectrometry (MS/MS) to identify analyte ions. The performance of the instrument is demonstrated by monitoring the ozonolysis reaction of a volatile organic compound producing aerosol particles. The aerosol QITMS is presented as an effective design for detection and analysis of aerosol compounds.
This work also describes the development of more efficient and informative MS/MS methods using infrared multiphoton photodissociation (IRMPD). IRMPD experiments are made practical for the QITMS by focusing the laser irradiation to increase photon flux on trapped ions. Efficient performance is used to increase sensitivity to product ions. Trapped ion clouds are profiled with higher resolution than previously obtained to characterize the effects of trapping parameters. IRMPD is also made selective by controlling the spatial distribution of ions relative to the laser pathway. More informative MS/MS spectra can be acquired without empirical determination of irradiation time, as is necessary for conventional IRMPD. The methods described use the fundamentals of ion trapping to design more effective photodissociation MS/MS experiments.
|Advisor:||Glish, Gary L.|
|Commitee:||Allbritton, Nancy L., Habibi, Sohrab, Jorgenson, James W., Schoenfisch, Mark H.|
|School:||The University of North Carolina at Chapel Hill|
|School Location:||United States -- North Carolina|
|Source:||DAI-B 71/01, Dissertation Abstracts International|
|Keywords:||Aerosols, Laser tomography, Quadrupole ion trap mass spectrometer, Tandem mass spectrometry|
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