Abstract
The compositions of explosives over the years have evolved as terrorists find new and creative ways to fabricate what are termed homemade, or improvised, explosive devices. As a result, routine methods used by defence and security laboratories for the targeted screening and identification of explosives and related compounds in casework samples become no longer appropriate. Solid phase extraction (SPE) for sample clean-up and target analyte preconcentration, followed by liquid chromatography-mass spectrometry (LC-MS) for separation and detection, is typically the method of choice for detecting trace organic explosives in complex sample types. The ‘matrix effect’ phenomenon, however, remains problematic and can lead to false negatives and even miscarriages of justice. A potential solution lies in a more effective sample preparation procedure. The aim of this work was to develop a novel SPE method, based on the principles of both selective extraction and exclusion, and combine it with 3D printing technology and high accuracy analysis, in order to provide a miniaturised, flexible solution to matrix effects in the analysis of organic explosives.In general, the established sample-dependent, dual-sorbent SPE procedures with existing commercial equipment provided the desired overall reduction in matrix effects, as well as increased selectivity and sensitivity, in the trace analysis of organic explosives from complex samples. The adaptation of multi-sorbent SPE to a 3D-printed version achieved performance metrics comparable with conventional SPE cartridges, as well as additional advantages including: (a) greater flexibility to be packed with the amount and sorbent chemistry of choice by the user, (b) potential to multiplex and modify parts to generate tailored arrays for a particular sample type, with no additional tubing or connecting parts, (c) low-cost and easy accessibility for laboratories, (d) on-demand nature, enabling rapid production of parts, as required, with no ordering delay, (e) low carbon footprint from removal of the requirement for delivery, (f) easy connection with syringes for on-site use, (g) good stability in a broad range of common organic solvents, which could allow application to extraction in other scientific fields, and (h) ability to both preserve the sample and speed up the overall analytical process chain.Furthermore, the successful application of the novel 3D-printed SPE approaches to real and simulated forensic scenarios proved its fitness for purpose. In particular, this approach provided increased assurance through enhanced removal of matrix and, ultimately, showed great promise for the compatible exploitation of additive manufacturing technology in sample preparation and, more generally, analytical chemistry.
| Date of Award | 1 Nov 2020 |
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| Original language | English |
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| Supervisor | Leon Barron (Supervisor) & Mark Parkin (Supervisor) |