An investigation into the suitability of time-of-flight mass spectrometry in forensic toxicology

Bloeck, Felix Richard Wolfgang (2016) An investigation into the suitability of time-of-flight mass spectrometry in forensic toxicology. MSc(R) thesis, University of Glasgow.

Abstract

Liquid chromatography coupled with mass spectrometry is one of the most powerful tools in the toxicologist’s arsenal to detect a wide variety of compounds from many different matrices. However, the huge number of potentially abused substances and new substances especially designed as intoxicants poses a problem in a forensic toxicology setting. Most methods are targeted and designed to cover a very specific drug or group of drugs while many other substances remain undetected.

High resolution mass spectrometry, more specifically time-of-flight mass spectrometry, represents an extremely powerful tool in analysing a multitude of compounds not only simultaneously but also retroactively. The data obtained through the time-of-flight instrument contains all compounds made available from sample extraction and chromatography, which can be processed at a later time with an improved library to detect previously unrecognised compounds without having to analyse the respective sample again.

The aim of this project was to determine the utility and limitations of time-of-flight mass spectrometry as a general and easily expandable screening method. The resolution of time-of-flight mass spectrometry allows for the separation of compounds with the same nominal mass but distinct exact masses without the need to separate them chromatographically.

To simulate the wide variety of potentially encountered drugs in such a general screening method, seven drugs (morphine, cocaine, zolpidem, diazepam, amphetamine, MDEA and THC) were chosen to represent this variety in terms of mass, properties and functional groups.

Consequently, several liquid-liquid and solid phase extractions were applied to urine samples to determine the most general suitable and unspecific extraction. Chromatography was optimised by investigating the parameters pH, concentration, organic solvent and gradient of the mobile phase to improve data obtained by the time-of-flight instrument. The resulting method was validated as a qualitative confirmation/identification method.

Data processing was automated using the software TargetAnalysis, which provides excellent analyte recognition according to retention time, exact mass and isotope pattern. The recognition of isotope patterns allows excellent recognition of analytes even in interference rich mass spectra and proved to be a good positive indicator.

Finally, the validated method was applied to samples received from the A& E Department of
Glasgow Royal Infirmary in suspected drug abuse cases and samples received from the
Scottish Prison Service, which we received from their own prevalence study targeting drugs
of abuse in the prison population. The obtained data was processed with a library established
in the course of this work.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Keywords: Forensic toxicology, drug screening, high resolution mass spectrometry
• Subjects: Q Science > Q Science (General); Q Science > QD Chemistry; R Medicine > RA Public aspects of medicine > RA1001 Forensic Medicine. Medical jurisprudence. Legal medicine
• Colleges/Schools: College of Medical Veterinary and Life Sciences
• Supervisor's Name: Torrance, Dr. Hazel
• Date of Award: 2016
• Depositing User: Felix Bloeck
• Unique ID: glathesis:2016-7768
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 10 Nov 2016 12:46
• Last Modified: 05 Dec 2016 11:49
• URI: https://theses.gla.ac.uk/id/eprint/7768