Analysis of Smokeless Powders, Smokeless Powder Residues, and Pyrolysis Products by GC-MS
Discipline: Chemistry and Chemical Sciences
Subcategory: Chemistry (not Biochemistry)
Session: 1
Room: Coolidge
Emily Lennert - University of Central Florida
Co-Author(s): Candice Bridge, Ph.D., University of Central Florida and National Center for Forensic Science, Orlando, FL
Following an explosive event, such as the detonation of an improvised explosive device or discharge of a firearm, partially burned or intact smokeless powder particles, as well as burned smokeless powder residues, may be recovered. Recovered particles or residues may then be analyzed and compared to a smokeless powder of known origin. The research presented herein may aid in providing a link between a suspect and a crime scene, and may be applicable to both organic gunshot residue analysis and analysis of debris after an explosive event. Intact and burned samples were analyzed to simulate real world evidence. Intact smokeless powders were extracted for Gas Chromatography – Mass Spectrometry (GC-MS) analysis through a simple extraction procedure set forth by the National Center for Forensic Science, using dichloromethane (DCM) and an internal standard of undecane. Smokeless powder residues were generated by burning of the smokeless powder. The residues were extracted from foil with approximately 2 mL DCM, followed by evaporation and reconstitution in 250 μL DCM with an n-tetracosane internal standard. Additionally, common smokeless powder compounds, such as nitroglycerin and methyl centralite, were burned in the presence of nitrocellulose (NC) to generate pyrolysis products for each compound individually. This allowed for comparison with smokeless powder residues. An individual sample of NC was also generated to determine pyrolysis products of NC that may be observed in all samples. The pyrolysis product residues were extracted in DCM. All extracts were analyzed via GC-MS to allow for identification of smokeless powder compounds and pyrolysis products present from each compound and in the smokeless powder residue. GC-MS parameters were optimized for each sample type prior to analysis. Organic compounds of interest were easily identified in smokeless powders, smokeless powder residues, and individual compound pyrolysis products. Pyrolysis product peak identification in smokeless powder residue extracts was aided by the data gathered from the individual compound pyrolysis products. The residue composition may then be related to the intact smokeless powder composition. Additionally, Pearson correlation coefficients were calculated between the smokeless powders and smokeless powder residues, as well as the smokeless powder residues and pyrolysis samples to determine the similarity in their resulting patterns. Future work includes analysis via Direct Analysis in Real Time – High Resolution Mass Spectrometry, as well as additional multivariate statistical methods for classification and comparison.
Funder Acknowledgement(s): This work is supported by the National Institute of Justice (NIJ) 2018-R2-CX-0008 and the State of Florida.
Faculty Advisor: Candice Bridge, Ph.D., cbridge@ucf.edu
Role: Conceptualization, Methodology, Investigation, Formal Analysis