March 2005 Meeting Announcement, Delaware Valley Mass Spectrometry Discussion Group
- Topic: "Gas Phase Ion/Molecule Reactions: A Limited View"
- Speaker: Burnaby Munson
- Date: Monday, March 14, 2005. 6:30 PM
- Time: Social Hour: 6:30 PM. (Pizza)
Talk: 7:30 PM.
- Place: Widener University, Webb Room
- Abstract: Ion/molecule reactions were nuisances in the development of mass spectrometry. H3+ was reported by Thomson by 1913. The presence of [M+H]+ ions in electron ionization spectra meant that isotope ratios were not always reliable. As vacuum technology and analytical mass spectrometers improved, the bi-molecular processes were more or less eliminated and forgotten until the 1950s when Tal'roze reported CH5+ in CH4 in the Soviet literature and Stevenson and Schissler (Shell) and Field, Franklin, and Lampe (Humble) began their studies in the US.
Early experiments in gas phase ion/molecule reactions were done in modified analytical mass spectrometers and occurred to small extents because the pressures were low (< 10-3 mm Hg) and the reaction times were short (~ s). Only very fast reactions, occurring at nearly every collision, could be observed. Subsequently, as instruments were built to operate at higher pressures and longer times, reactions could be studied to large extents of conversion, consecutive reactions were observed, and equilibrium conditions achieved.
As source pressures were increased, the effects of small concentrations of impurities were (re-)discovered and chemical ionization mass spectrometry, CIMS, was developed as an analytical application of ion/molecule reactions. CIMS and GC/CIMS are now routine analytical techniques. CI mass spectra are often less complex than EI mass spectra and CIMS is frequently used for quantitation in complex mixtures. GC/CIMS with selective reactant ions can be used to identify different classes of compounds. GC/CIMS is a convenient way to study the ion chemistry of complex, but volatile, molecules.
- Bio: Burnaby Munson obtained his Ph. D. from the University of Texas (Austin) in 1959 and worked at the Research & Development Division of the Humble Oil & Refining Co. (Baytown, Texas), which became part of Esso Research & Engineering Co (then Exxon and now Exxon-Mobil) until 1967, when he joined the Chemistry (now Chemistry & Biochemistry) Department of the University of Delaware. He began research in gas phase ion chemistry with (the late) Joe L. Franklin and Frank H. Field in 1962. With Frank Field, he developed Chemical Ionization Mass Spectrometry. His research at the University of Delaware has involved kinetics, thermochemistry, and analytical applications of ion/molecule reactions
- Directions: See Web Page at: http://science.widener.edu/svb/msdg/
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