Qi, Yulin (2013) Advanced methods in fourier transform ion cyclotron resonance mass spectrometry. PhD thesis, University of Warwick.

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Abstract

Mass spectrometry (MS) is a powerful analytical technique used to
characterize various compounds by measuring the mass-to-charge ratio (m/z).
Among different types of mass analyzers, Fourier transform ion cyclotron
resonance mass spectrometer (FT-ICR MS) is the instrument of choice for
those working at the forefront of research, as it offers incomparable mass
accuracy, resolving power, and the highest flexibility for hybrid instrumentation
and fragmentation techniques.
The FT-ICR MS requires professional and careful tuning to achieve its
superior performance. Our work aims to review, develop and apply advanced
methods to improve the data quality of FT-ICR and push the limits of the
instrument.
FT-ICR spectrometry has been limited to the magnitude-mode for 40 years
due to the complexity of the phase-wrapping problem. However, it is well known
that by correcting phase of the data, the spectrum can be plotted in the
absorption-mode with a mass resolving power that is as much as two times
higher than conventional magnitude-mode. Based on the assumption that the
frequency sweep excitation produces a quadratic accumulation in an ion’s
phase value, a robust manual method to correct all ions’ phase shifts has been
developed, which allows a broadband FT-ICR spectrum to be plotted in the
absorption-mode.
The developed phasing method has then been applied to a large variety of
samples (peptides, proteins, crude oil), different spectral acquisition-mode
(broadband, narrowband), and different design of ICR cells (Infinity cell, ParaCell) to compare the performance with the conventional magnitude-mode
spectra. The outcome shows that, by plotting the absorption-mode spectrum,
not only is the spectral quality improved at no extra cost, but the number of
detectable peaks is also increased. Additionally, it has been found that
artifactual peaks, such as noise or harmonics in the spectrum can be
diagnosed immediately in the absorption-mode.
Given the improved characteristics of the absorption-mode spectrum, the
following research was then focused on a data processing procedure for phase
correction and the features of the phase function. The results demonstrate that
in the vast majority of cases, the phase function needs to be calculated just
once, whenever the instrument is calibrated. In addition, an internal calibration
method for calculating the phase function of spectra with insufficient peak
density across the whole mass range has been developed. The above
research is the basis of the Autophaser program which allows spectra
recorded on any FT-ICR MS to be phase corrected in an automated manner.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QD Chemistry
Library of Congress Subject Headings (LCSH):	Ion cyclotron resonance spectrometry, Fourier transform spectroscopy
Official Date:	April 2013
Dates:	Date Event April 2013 Submitted
Institution:	University of Warwick
Theses Department:	Department of Chemistry
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	O'Connor, Peter B.
Sponsors:	University of Warwick. Department of Chemistry; Engineering and Physical Sciences Research Council (EPSRC) (EP/F034210/1)
Extent:	xxv, 240 leaves : illustrations.
Language:	eng

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