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B.A., 2005, Concordia University Irvine,
Chemistry and Mathematics Evan developed an "Ambient Pressure Pyroelectric Ion Source for Mass Spectrometry," and a preliminary account is recently published (Neidholdt, E.L.; Beauchamp, J.L. Anal. Chem. 2007, 79, 3945-3948). Abbreviated APPIS, It is a novel ionization source with promising characteristics. It differs from traditional ion sources in its simplicity and robust design. The source comprises a z-cut pyroelectric crystal (lithium niobate or lithium tantalate) with an attached resistive heating element. Thermally cycling the crystal by as little as 30 K from ambient gives rise to tremendous electrical potentials on the z- faces of the crystal. The source has been shown capable of ionizing acidic and basic species by deprotonation or protonation (respectively). Current work explores the true ionization mechanism, with efforts to distinguish possible gas phase chemical ionization processes from reactions with the crystal surface. The source consumes very little power, and is particularly durable, making it suitable for a number of harsh environments. Another part of Evan's work involves studies
of non-covalently bound gas
phase clusters, specifically clusters of benzoic acid with the alkaline
earth metal cations magnesium, calcium, strontium, and barium. Through
decarbonylation of benzoate anion, phenide anion (C6H5-)
is obtained, allowing for studies with one of the simplest of aromatic
nucleophiles. Of particular interest are reactions of
organomagesium complexes such as phenylmagnesium, as similar species
have been shown to be reactive in the gas phase. Lastly, Evan is involved in the continuation of the Free Radical Initiated Peptide Sequencing (FRIPS) project initiated by former group members Heather Cox and Rob Hodyss. This project examines the suitability for use in proteomics of certain commercially available free radical initiators. These radical initiators cleave peptides differently than tryptic digests or Edman degradation, and show the potential for a tunable peptide sequencing tool. A series of model peptides, with the general formula AARAAAXAA where X is any one of the 20 amino acids, has been investigated using the FRIPS methodology. Distinct reactivity classes emerge, allowing for the customization of reaction via these free radical reactions. |
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Beauchamp Research
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