Forensic analysis of explosives using isotope ratio mass spectrometry (IRMS) — Discrimination of ammonium nitrate sources

Benson, Sarah J.; Lennard, Christopher J.; Maynard, Philip; Hill, David M.; Andrew, Anita S.; Roux, Claude

doi:10.1016/j.scijus.2009.04.005

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Volume 49, Issue 2 , Pages 73-80, June 2009

Forensic analysis of explosives using isotope ratio mass spectrometry (IRMS) — Discrimination of ammonium nitrate sources

Sarah J. Benson
- Forensic & Data Centres, Australian Federal Police, GPO Box 401, Canberra 2601, ACT, Australia
- Centre for Forensic Science, University of Technology, Sydney, PO Box 123, Broadway 2007, NSW, Australia
- Corresponding author. Australian Federal Police, GPO Box 401, Canberra 2601, ACT, Australia. Tel.: +61 2 6223 3386; fax: +61 2 6223 3270.
Christopher J. Lennard
- Forensic & Data Centres, Australian Federal Police, GPO Box 401, Canberra 2601, ACT, Australia
- National Centre for Forensic Studies, University of Canberra, Canberra 2601, ACT, Australia
Philip Maynard
- Centre for Forensic Science, University of Technology, Sydney, PO Box 123, Broadway 2007, NSW, Australia
David M. Hill
- Australian Nuclear Science and Technology Organisation, PMB 1, Menai 2234, NSW, Australia
Anita S. Andrew
- Environmental Isotopes Pty. Ltd., PO Box 1492, Macquarie Centre 2113, NSW, Australia
Claude Roux
- Centre for Forensic Science, University of Technology, Sydney, PO Box 123, Broadway 2007, NSW, Australia

Received 22 November 2008; received in revised form 6 April 2009; accepted 6 April 2009. published online 25 May 2009.

Abstract

An evaluation was undertaken to determine if isotope ratio mass spectrometry (IRMS) could assist in the investigation of complex forensic cases by providing a level of discrimination not achievable utilising traditional forensic techniques. The focus of the research was on ammonium nitrate (AN), a common oxidiser used in improvised explosive mixtures.

The potential value of IRMS to attribute Australian AN samples to the manufacturing source was demonstrated through the development of a preliminary AN classification scheme based on nitrogen isotopes. Although the discrimination utilising nitrogen isotopes alone was limited and only relevant to samples from the three Australian manufacturers during the evaluated time period, the classification scheme has potential as an investigative aid.

Combining oxygen and hydrogen stable isotope values permitted the differentiation of AN prills from three different Australian manufacturers. Samples from five different overseas sources could be differentiated utilising a combination of the nitrogen, oxygen and hydrogen isotope values. Limited differentiation between Australian and overseas prills was achieved for the samples analysed.

The comparison of nitrogen isotope values from intact AN prill samples with those from post-blast AN prill residues highlighted that the nitrogen isotopic composition of the prills was not maintained post-blast; hence, limiting the technique to analysis of un-reacted explosive material.

Keywords: Stable isotopes, Ammonium nitrate, Explosives, Isotope ratio mass spectrometry, IRMS