The majority of the work described in this thesis has involved the development and application of two-step mass spectrometry for the <i>in situ</i> analysis of priority pollutants. With this approach - laser desorption laser photoionisation mass spectrometry, abbreviated here as L2MS - a pulsed (infrared, visible or UV) laser is used to desorb neutral molecules which are then positioned using a second pulsed (UV) laser. The resulting product photoions are then analysed using time-of-flight mass spectrometer. A detailed comparison of L2MS versus other mass spectrometric techniques for the analysis of environmental samples has been carried out. The underlying physical principles behind L2MS are described, together with the instrumentation used and the experimental procedures and protocols that were developed. The majority of the work presented has focused on the polycyclic aromatic hydrocarbons (PAHs) and related compounds directly from their host matrices, photoionisation at a wavelength of 193 nm or 266 nm. The matrices investigated included soils, sediments, extracts and aerosol particulates. Although, these samples were part of a complex system the selectivity inherent in L2MS enabled simple mass spectra to be obtained, showing each PAH as a molecular ion. A number of experiments have been carried out using certified reference materials to investigate the reproducibility of the spectra generated and the feasibility of using L2MS for quantitative as well as semi-quantitative studies on "real-world" samples. In parallel with this work, the same reference materials have been interrogated using a variety of other analytical techniques, such as gas chromatography mass spectrometry (GC MS), field desorption mass spectrometry (FD MS), laser desorption/ionisation mass spectrometry (LD1 MS), and high performance liquid chromatography (HPLC). These techniques, together with L2MS, were applied to analyse both the intact samples ("<i>in situ</i>" studies) and Soxhlet extracts. Using GCMS and HPLC enabled the identification of most of the PAHs present in the extracts. Whereas, FD was found to produce a complex spectra which was difficult to interpret. Finally LDI MS could prove to be useful for screening, as sample preparation and production of a spectra is simple. However, under the ionisation wavelength employed, 337 nm, during this work spectra were difficult to produce.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:659699 |
| Date | January 1999 |
| Creators | Mudge, Angela |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/15448 |
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