title: Isotopic and elemental profiling of ammonium nitrate in forensic explosives investigations.
abstract: Ammonium nitrate (AN) is frequently encountered in explosives in forensic casework. It is widely available as fertilizer and easy to implement in explosive devices, for example by mixing it with a fuel. Forensic profiling methods to determine whether material found on a crime scene and material retrieved from a suspect arise from the same source are becoming increasingly important. In this work, we have explored the possibility of using isotopic and elemental profiling to discriminate between different batches of AN. Variations within a production batch, between different batches from the same manufacturer, and between batches from different manufacturers were studied using a total of 103 samples from 19 different fertilizer manufacturers. Isotope-ratio mass spectrometry (IRMS) was used to analyze AN samples for their (15)N and (18)O isotopic composition. The trace-elemental composition of these samples was studied using inductively coupled plasma-mass spectrometry (ICP-MS). All samples were analyzed for the occurrence of 66 elements. 32 of these elements were useful for the differentiation of AN samples. These include magnesium (Mg), calcium (Ca), iron (Fe) and strontium (Sr). Samples with a similar elemental profile may be differentiated based on their isotopic composition. Linear discriminant analysis (LDA) was used to calculate likelihood ratios and demonstrated the power of combining elemental and isotopic profiling for discrimination between different sources of AN.
authors.affiliation: University of Amsterdam, van 't Hoff Institute for Molecular Sciences, PO Box 94157, 1090 GD Amsterdam, The Netherlands; Netherlands Forensic Institute, PO Box 24044, 2490 AA The Hague, The Netherlands; TNO Defence, Security and Safety, PO Box 45, 2280 AA Rijswijk, The Netherlands. Electronic address: hannekebrust@gmail.com.
authors.forename: Hanneke
authors.initials: H
authors.lastname: Brust
authors.affiliation: Netherlands Forensic Institute, PO Box 24044, 2490 AA The Hague, The Netherlands. Electronic address: m.koeberg@nfi.minvenj.nl.
authors.forename: Mattijs
authors.initials: M
authors.lastname: Koeberg
authors.affiliation: TNO Defence, Security and Safety, PO Box 45, 2280 AA Rijswijk, The Netherlands; Delft University of Technology, PO Box 5, 2600 AA Delft, The Netherlands. Electronic address: antoine.vanderheijden@tno.nl.
authors.forename: Antoine
authors.initials: A
authors.lastname: van der Heijden
authors.affiliation: Netherlands Forensic Institute, PO Box 24044, 2490 AA The Hague, The Netherlands. Electronic address: w.wiarda@nfi.minvenj.nl.
authors.forename: Wim
authors.initials: W
authors.lastname: Wiarda
authors.affiliation: Netherlands Forensic Institute, PO Box 24044, 2490 AA The Hague, The Netherlands.
authors.forename: Ines
authors.initials: I
authors.lastname: Mügler
authors.affiliation: Netherlands Forensic Institute, PO Box 24044, 2490 AA The Hague, The Netherlands. Electronic address: m.schrader@nfi.minvenj.nl.
authors.forename: Marianne
authors.initials: M
authors.lastname: Schrader
authors.affiliation: University of Amsterdam, van 't Hoff Institute for Molecular Sciences, PO Box 94157, 1090 GD Amsterdam, The Netherlands. Electronic address: g.vivotruyols@uva.nl.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Vivo-Truyols
authors.affiliation: University of Amsterdam, van 't Hoff Institute for Molecular Sciences, PO Box 94157, 1090 GD Amsterdam, The Netherlands. Electronic address: p.j.schoenmakers@uva.nl.
authors.forename: Peter
authors.initials: P
authors.lastname: Schoenmakers
authors.affiliation: University of Amsterdam, van 't Hoff Institute for Molecular Sciences, PO Box 94157, 1090 GD Amsterdam, The Netherlands; Netherlands Forensic Institute, PO Box 24044, 2490 AA The Hague, The Netherlands; CLHC, Amsterdam Center for Forensic Science and Medicine, PO Box 94157, 1090 GD Amsterdam, The Netherlands. Electronic address: a.van.asten@nfi.minvenj.nl.
authors.forename: Arian
authors.initials: A
authors.lastname: van Asten
mesh_terms: D016002:Discriminant Analysis; D053834:Explosive Agents / Q000737:chemistry*; D044707:Forensic Sciences; D016013:Likelihood Functions; D013058:Mass Spectrometry / Q000379:methods; D009566:Nitrates / Q000737:chemistry*; D009587:Nitrogen Isotopes / Q000032:analysis; D010103:Oxygen Isotopes / Q000032:analysis; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D053834:Explosive Agents; D009566:Nitrates; D009587:Nitrogen Isotopes; D010103:Oxygen Isotopes; C006568:ammonium nitrate
keywords: (laser ablation–) inductively coupled plasma–mass spectrometry; Ammonium nitrate; Chemical profiling; Explosive; Isotope-ratio mass spectrometry; Likelihood ratios