Measurement of atmospheric volatile organic compounds with proton transfer reaction- mass spectrometry

The instrument employed in this study was a PTR-MS with switchable reagent ion capability (SRI-MS), which enables the use of O₂⁺ and NO⁺ as reagent ions in addition to H₃O⁺. The application of SRI-MS to measurements of inorganic and organic compounds in the atmosphere is still in its infancy and studies such as those reported here are critical to determine what, if any, additional information can be acquired through the use of reagent ions other than H₃O⁺. The laboratory studies described in this thesis represent one of the most extensive characterizations of the performance of SRI-MS instruments for the identification and quantification of volatile organic compounds (VOCs) to date. This was followed by one of the first real-world comparisons of the measurement of VOCs using O₂⁺, NO⁺ and H₃O⁺ reagent ions in SRI-MS and this work represents a significant contribution to the available information on the application of SRI-MS to atmospheric observations of VOCs. In addition, two novel applications of SRI-MS were developed: A study of acetonitrile showed that in some cases corrections may be made for the coincidence of several VOC signals at the same mass/charge ratio, and an improved analyte signal obtained. Finally some promising results concerning the measurement of total non-methane organic carbon with SRI-MS were presented.