Targeted and non-targeted forensic profiling of black powder substitutes and gunshot residue using gradient ion chromatography – high resolution mass spectrometry (IC-HRMS)

TY - JOUR

T1 - Targeted and non-targeted forensic profiling of black powder substitutes and gunshot residue using gradient ion chromatography – high resolution mass spectrometry (IC-HRMS)

AU - Gallidabino, Matteo

AU - Irlam, Rachel

AU - Salt, Michael

AU - O'Donnell, Michael

AU - Beardah, Matthew

AU - Barron, Leon

N1 - Funding Information: This work was approved by the BDM Research Ethics Subcommittee of King’s College London (reference no. HR-15/16-1962 and HR-17/18-4078), and kindly supported by the Swiss National Science Foundation (grant no. P2LAP1_164912 ). The authors would like to thank Bronagh Murphy (King's College London, UK) for her advice and assistance with method development and application to fingermark analysis, as well as Dr. William Cheung (Northumbria University, Newcastle upon Tyne, UK) for his help in non-targeted analysis. Further thanks are extended to the team of the Mass Spectrometry Facility of King's College London for providing the Orbitrap instrument and technical support, as well as to Andrew Osborne, Jonathan Bruce, Andy Matthews, Andrea Wille and Katinka Ruth (Metrohm AG, Herisau, Switzerland) for the loan and support of the IC instrument. Publisher Copyright: © 2019 Elsevier B.V.

PY - 2019/9/23

Y1 - 2019/9/23

N2 - A novel and simplified gradient IC-HRMS approach is presented in this work for forensic profiling of ionic energetic material residues, including low-order explosives and gunshot residue (GSR). This new method incorporated ethanolic eluents to facilitate direct coupling of IC and HRMS without auxiliary post-column infusion pumps that are traditionally used to assist with gas phase transfer. Ethanolic eluents also enabled better integration with an in-service protocol for direct analysis of high-order organic explosives by IC-HRMS, without requiring solvent exchange before injection. Excellent method performance was achieved, enabling both full scan qualitative and quantitative analysis, as required. In particular, linearity for 19 targeted compounds yielded R2 > 0.99 across several orders of magnitude, with trace analysis possible at the low-mid pg level. Reproducibility and mass accuracies were also excellent, with peak area %RSDs <10%, tR %RSDs <0.4% and δm/z < 3 ppm. The method was applied to targeted analysis of latent fingermarks and swabbed hand sweat samples to determine contact with a black-powder substitute containing nitrate, benzoate and perchlorate. When combined with principal component analysis (PCA), the effect of time since handling on recorded signals could be interpreted further in order to support forensic investigations. In a second, non-targeted application, PCA using full scan IC-HRMS data enabled classification of GSR from three different types of ammunition. An additional 20 markers of GSR were tentatively identified in silico, in addition to the 15 anions detected during targeted analysis. This new approach therefore streamlines and adds consistency and flexibility to forensic analysis of ionic energetic material. Furthermore, it also has implications for targeted, non-targeted and suspect screening applications in other fields by expanding the separation space to low molecular weight inorganic and organic anions.

AB - A novel and simplified gradient IC-HRMS approach is presented in this work for forensic profiling of ionic energetic material residues, including low-order explosives and gunshot residue (GSR). This new method incorporated ethanolic eluents to facilitate direct coupling of IC and HRMS without auxiliary post-column infusion pumps that are traditionally used to assist with gas phase transfer. Ethanolic eluents also enabled better integration with an in-service protocol for direct analysis of high-order organic explosives by IC-HRMS, without requiring solvent exchange before injection. Excellent method performance was achieved, enabling both full scan qualitative and quantitative analysis, as required. In particular, linearity for 19 targeted compounds yielded R2 > 0.99 across several orders of magnitude, with trace analysis possible at the low-mid pg level. Reproducibility and mass accuracies were also excellent, with peak area %RSDs <10%, tR %RSDs <0.4% and δm/z < 3 ppm. The method was applied to targeted analysis of latent fingermarks and swabbed hand sweat samples to determine contact with a black-powder substitute containing nitrate, benzoate and perchlorate. When combined with principal component analysis (PCA), the effect of time since handling on recorded signals could be interpreted further in order to support forensic investigations. In a second, non-targeted application, PCA using full scan IC-HRMS data enabled classification of GSR from three different types of ammunition. An additional 20 markers of GSR were tentatively identified in silico, in addition to the 15 anions detected during targeted analysis. This new approach therefore streamlines and adds consistency and flexibility to forensic analysis of ionic energetic material. Furthermore, it also has implications for targeted, non-targeted and suspect screening applications in other fields by expanding the separation space to low molecular weight inorganic and organic anions.

KW - Explosive analysis

KW - Fingermarks

KW - Forensic science

KW - High resolution mass spectrometry

KW - Ion chromatography

KW - Non-targeted analysis

UR - http://www.scopus.com/inward/record.url?scp=85065977420&partnerID=8YFLogxK

U2 - 10.1016/j.aca.2019.04.048

DO - 10.1016/j.aca.2019.04.048

M3 - Article

C2 - 31146860

AN - SCOPUS:85065977420

SN - 0003-2670

VL - 1072

SP - 1

EP - 14

JO - ANALYTICA CHIMICA ACTA

JF - ANALYTICA CHIMICA ACTA

ER -