The development of chromatographic methods for the detection of low molecular weight organic acids and inorganic anions found in low-order explosive residues are presented. The work is divided into six sections. Firstly, Chapter 1 provides a background on low-order explosives and fingermarks. Existing methods for the analysis of these sample types, focussing on ion chromatography (IC) and mass spectrometry (MS) technologies, are reviewed. Gaps in knowledge are highlighted and the aims and objectives of the thesis presented and justified towards addressing these challenges. Chapter 2 applies an anion exchange chromatographic method for the analysis of gunshot residue. This micro-bore scale method utilises a hydroxide gradient with suppressed conductivity detection. A study on external contamination, such as from environmental matrices and collection devices, is presented suggesting that direct extraction of the residues is more advantageous for the analysis of these residues on small items. Analytical performance characteristics for linearity, repeatability and limits of detection are also presented and discussed. Chapter 3 extends the performance limits of IC by investigating the use of capillary-scale IC technology for the detection of low-order explosive residues for the first time, including gunshot residues and black powder substitutes, in biological matrices such as sweat and human latent fingermarks. A comparison to the micro-bore method in Chapter 2 is made, with a focus on the measured increase in absolute sensitivity at the lower limits. In a brief study, a capillary-scale organic polymer monolithic resin (IonSwift MAX-100) was also investigated in terms of backpressure and efficiency. Chapter 4 presents the selectivity offered by alternative anion exchange resins with the addition of organic solvents to the eluent, specifically methanol and acetonitrile. The combined effect of temperature and organic solvent-containing eluents on IC selectivity is also presented for the first time and discussed regarding their use as variables in IC method development. Analytical performance characteristics for linearity, repeatability and limits of quantification are presented. Chapter 5 combines the organic solvent and temperature-enhanced IC method developed in Chapter 4 with high resolution mass spectrometry (HRMS) detection which enabled simplified coupling of these two technologies. The method was applied to the forensic detection of low-order explosives in fingermarks for the first time, offering confirmatory analysis of several forensically important species at pg amounts. Analytical performance characteristics for linearity, repeatability and limits of quantification are once again presented and compared to the published literature. Chapter 6 presents results collected by capillary electrophoresis and Raman spectroscopy as alternative/complementary techniques to IC. These techniques are applied to the detection of explosive residues in biological matrices, and their relative merits are discussed. The development of several IC-based technologies enabled the successful interrogation of small anions in low-order explosives within fingermarks at fg-ng amounts for the first time, offering the potential to link identity with criminal activity. In particular, the development of a solvent enhanced-IC method with simplified coupling to HRMS shows considerable benefit not just for forensic purposes, but for IC applications in a number of alternative fields.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:669563 |
| Date | January 2015 |
| Creators | Gilchrist, Elizabeth Sarah |
| Contributors | Barron, Leon Patrick; Smith, Norman William |
| Publisher | King's College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://kclpure.kcl.ac.uk/portal/en/theses/ion-chromatography-and-ion-chromatographyhigh-resolution-mass-spectrometry-technologies-for-the-analysis-of-loworder-explosive-residues(8b6c406d-97f2-4fe3-9739-0decc5ef26d3).html |
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