Stable isotope analysis
: A new forensic science tool

  • Lisa Reidy

Student thesis: Doctoral ThesisDoctor of Philosophy


The principle behind forensic analysis is to acquire information previously unknown, or to corroborate information available on either a samples' origin, or a comparative analysis. Conventional analytical techniques used in the analysis of forensic chemical samples include Gas and Liquid Chromatography-Mass Spectrometry, infrared spectroscopy, thin layer chromatograph. In recent years, the development of the analytical technique isotope ratio mass spectrometry (IRMS) has increased the information obtainable regarding sample origin and history.

Investigations were carried out on white paint samples using Elemental Analysis Isotope Ratio Mass Spectrometry (EA-IRMS) to determine the discriminatory capabilities of this technique on a simple chemical sample. The results demonstrated the possible application ofEA-IRMS to chemical samples.

In the 1980's the phenomenon of so-called designer drugs was fully recognised in the UK. The prevalence of drugs such as MDMA or 'ecstasy' has increased rapidly in Northern Ireland. In order to establish shipping routes and link batches to countries of production, current analysis of synthetic drugs requires a focus on more comprehensive profile of seized tablets. In this thesis, experimental studies using Elemental Analysis Isotope Ratio Mass Spectrometry (EA-IRMS) to analyse seized ecstasy tablets from different geographical locations are presented. Isotopic analysis has increasingly been used to obtain information on the geographical origin of production of natural illicit drugs. By examining the 'bulk' isotopic profile of seized illicit drugs, i.e. the complete sample, it is possible to distinguish distinct batches of ecstasy tablets with a large isotopic range seen in all four isotopes. Seizures of ecstasy tablets from Northern Ireland showed a range of 02H and o15N of 45%o and 6%o respectively across all twelve seizures allowing the separation of all batches. When analysing o13C values across all 41 seizures submitted for analysis the range was much larger at l l .6%0 demonstrating that the bulk isotope profile was varied with seizure, that can be exploited in the profiling of ecstasy tablets. However, the results presented are unable to determine the country of seizure from the 'bulk' isotope profile.

Bulk isotope profiling was carried out on precursors and adulterants to establish if the isotope profile of these ingredients in ecstasy tablets could provide any information on the geographical origin of production of ecstasy tablets or further the discrimination capabilities of IRMS on illicit drug samples. The results presented in this thesis demonstrate that the isotope profile of paracetamol, common adulterants in illicit drugs, may provide additional discrimination capabilities for different seizures depending on the paracetamol product used in production of ecstasy. However, the geographical origin of these samples is still unclear when analysing the bulk isotope profile. The extraction of the active ingredient of the paracetamol tablets (acetaminophen) was performed and then isotopically analysed using EA-IRMS. It was found that the isotope profile of the acetaminophen did provided limited information on the geographical origin of the sample, and hence the concept of using the paracetamol to determine the country of production for ecstasy is not possible.

Isotopic analysis of the active ingredient m the seized ecstasy tablet, methylenedioxymethamphetamine (MDMA), is presented in this thesis using Gas Chromatography Isotope ratio Mass Spectrometry (GC-IRMS). This was carried out to determine if the difference in the bulk isotopic signature of the ecstasy tablets was due to differences in the isotope profile of the MDMA, and also to determine if any additional discriminatory power was available using GC-IRMS. The range of 13C/12C profiles was narrow ( 4.1 %0) across all 41 seizures analysed, and therefore could not account for the range seen in the bulk isotope profile of these tablets. However, it did provide some discriminatory power to separate similar bulk isotopic seizures based on the 13C/12C isotope profile of the MDMA.

Investigations were carried out in this thesis on amphetamine samples with a known synthesis history, but unknown seizure patterns. It was found that by using EA-IRMS it was possible to determine the seizures based on the isotopic profile of the samples, with only two samples falling outside the groups. This investigation concluded that even when the synthesis method is the same there is still variation in the bulk 15N/14N and 13C/12C isotope profile of amphetamine samples.

Overall in can be concluded that the use of isotope profiling on chemical sample encountered in forensic laboratories may provide discrimination capabilities that other techniques can not provide.
Date of AwardJul 2007
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SupervisorBob Kalin (Supervisor)

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