Ion dynamics in the orbitrap mass analyzer and investigations into the chiral amplification of serine upon sublimation
Abstract
Since its introduction, the orbitrap has proven to be a robust mass analyzer that can routinely deliver high resolving power and mass accuracy. Unlike conventional ion traps such as the Paul and Penning traps, the orbitrap uses only electrostatic fields to confine and to analyze injected ion populations. In addition, its relatively low cost, simple design and high space-charge capacity make it suitable for tackling complex scientific problems in which high performance is required. Research on the orbitrap in our laboratory is aimed at developing a deeper theoretical understanding of the dynamics of confined ion populations. This work is relevant to improving performance characteristics (e.g., resolution and mass accuracy), developing novel ion motion control (IMC) techniques and applications, designing new instrumentation, and implementing tandem mass spectrometry (MS/MS) capabilities inside the orbitrap.^ This dissertation offers a brief introduction to the fundamental principles of the orbitrap mass analyzer (Chapter 1) and describes experiments that advance the research goals outlined above. Experiments include: (a) characterization of a prototype storage quadrupole (StQ)-Orbitrap spectrometer (Chapter 2); (b) application of IMC techniques to improve performance (resolution and mass accuracy) via rephrasing of confined ion populations (Chapter 3); and (c) studies of space charge mediated processes such as mass shifts and peak coalescence (Chapter 4).^ The second subject area covered in this dissertation (Chapter 5) is the investigation of the chiral amplification of serine upon sublimation. This experiment is of importance because homochirality is believed to be a prerequisite for the origin of life. So, when previous mass spectrometry-based studies revealed that serine produces a stable, homochiral octameric cluster, it was proposed that this amino acid may play a role in homochirogenesis. To evaluate this hypothesis, non-mass spectrometric experiments were developed. Here we report that non-racemic samples of serine, with a small enantiomeric excess (e.e.), when heated to moderate temperatures (175°C – 230°C) in an inert N2 atmosphere, sublime to give serine that is enriched in the major enantiomer. The results prove that spontaneous resolution of amino acids (specifically serine) upon sublimation is a natural phenomenon i.e., the process occurs in the ambient environment under mild conditions.^
Degree
Ph.D.
Advisors
Robert G. Cooks, Purdue University.
Subject Area
Chemistry, General|Chemistry, Analytical|Chemistry, Physical
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