A computer program to simulate peak shapes from time-of-flight (TOF) mass spectrometers has been developed and significantly improved from a previous, unpublished version. This program can accurately simulate both TOF and orthogonal acceleration TOF mass analyser peak shapes, with contributions from initial ion properties, instrument geometry, and other factors including high voltage ripple and detector response. Grid effects have also been included, and simulations for two mass spectrometers are compared to actual recorded spectra. The dispersive effect on ion trajectories of parallel wires and grids has been computationally studied and a model derived for each case. The model is based on the effect wire geometry has on the intrinsic focussing effect of the grid. The models for parallel wires and rectangular grids have been coded into the simulation program described above, and the effect of grids on peak shapes in TOF mass spectrometers has been studied. Good correlation between simulated and actual peak shapes for rectangular grids was obtained for grids in different rotational orientations. A pulsed lens has been developed to reduce the velocity spread of ions in matrix assisted laser desorption/ionisation (MALDI) ion sources, with the aim to increase sensitivity in orthogonal acceleration TOF mass analysers. The system gave an increase in sensitivity of approximately five times over a range of masses, however instrument resolving power was reduced. A rotating sample stage was developed for MALDI mass spectrometers which offers the potential of high sample density, high positional accuracy and repeatability, and low seek times. The system involves reading the position of a disk mounted with MALDI sample spots and timing the laser pulse to coincide with spot availability at an aperture. The system was successfully used to perform mass calibration by using a calibrant sample located on a separate spot to the analyte. Mass resolved disk imaging was also performed over a disk radius using inks. The mass resolved image compared well to the optical image.
| Identifer | oai:union.ndltd.org:ADTP/234925 |
| Date | January 2006 |
| Creators | Lewin, Mark James, Chemistry, Faculty of Science, UNSW |
| Publisher | Awarded by:University of New South Wales. |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Lewin Mark James., http://unsworks.unsw.edu.au/copyright |
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