Laser Desorption Ionisation of forensically significant samples. An investigation into low mass analysis

Author: Rachel West

West, Rachel, 2021 Laser Desorption Ionisation of forensically significant samples. An investigation into low mass analysis, Flinders University, College of Science and Engineering

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Forensically significant samples, such as drugs and propellants can be analysed using a range of standard techniques like Hight Performance Liquid Chromatography (HPLC) and Gas Chromatography Mass Spectrometry (GCMS). These methods can often be time-consuming, require complex sample preparation or extraction, with multiple steps and additional components. The drug samples investigated are those that have been inlaid in fibres, in this form to either mimic oral fluid based roadside drug tests or drug laden clothing and other fabrics used in smuggling cases. The analysis of these samples is important and can be complicated by the need for extraction of the analytes from the fibres and the possible destruction of evidence required to perform said analysis.

Laser Desorption Ionization (LDI) techniques are an intriguing alternative to these standard techniques as they can perform high throughput analysis with little sample preparation and often generate simple spectra. LDI is highly sensitive and specific and is compatible with less stable sample-types.

The initial issue for LDI analysis of drug samples was associated with low mass interference experienced when such low mass analytes encounter similar mass matrices. Several alternatives to traditional matrices were explored, and it was successfully overcome for on-plate and fibre-based analyses using a layer of gold nanomaterials which provided increased laser absorption without the low mass interference.

LDI was also explored as a method of analysing complex propellant samples. Propellants contain several different species, which vary among manufacturers and as samples age. They often require multiple techniques for their analysis with different sample preparation techniques. LDI was compared to standard techniques as well as some more interesting alternatives, to successfully differentiate several diverse propellant samples.

Keywords: laser desorption ionisation, drugs, energetic materials, mass spectrometry, nanoparticles

Subject: Chemistry thesis

Thesis type: Doctor of Philosophy
Completed: 2021
School: College of Science and Engineering
Supervisor: Stewart Walker