Study of the Behaviors of Gunshot Residues from Spent Cartridges by Headspace Solid-Phase Microextraction-Gas Chromatographic Techniques.

Gunshot residues, produced after shooting activity, have acquired their importance in analysis due to the notoriety of firearms-related crimes. In this study, solid-phase microextraction was performed to extract the headspace composition of spent cartridges using 85-µm polyacrylate fiber at 66°C for 21 min. Organic compounds, that is, naphthalene, 2,6-dinitrotoluene, 2,4-dinitrotoluene, diphenylamine, and dibutyl phthalate were detected and analyzed by gas chromatography-flame ionization detection technique. Evaluation of chromatograms for diphenylamine, dibutyl phthalate, and naphthalene indicates the period after a gunshot was discharged, whether it was 1 days, 2-4 days, <5 days, 10 days, 20 days, or more than 30 days ago. This study revealed the potential effects of environmental factors such as occasional wind blow and direct sunlight on the estimation of time after spent cartridges were discharged. In conclusion, we proposed reliable alternative in analyzing the headspace composition of spent cartridges in a simulated crime scene.

Optimization of headspace solid-phase microextraction technique for extraction of volatile smokeless powder compounds in forensic applications.

Smokeless powders are low explosives and are potentially found in cases involving firearms and improvised explosive devices. Apart from inorganic compound analysis, forensic determination of organic components of these materials appears as a promising alternative, especially the chromatographic techniques. This work describes the optimization of a solid-phase microextraction technique using an 85 µm polyacrylate fiber followed by gas chromatography-flame ionization detection for smokeless powder. A multivariate experimental design was performed to optimize extraction-influencing parameters. A 2(4) factorial first-order design revealed that sample temperature and extraction time were the major influencing parameters. Doehlert matrix design has subsequently selected 66°C and 21 min as the compromised conditions for the two predetermined parameters. This extraction technique has successfully detected the headspace compounds of smokeless powders from different ammunition types and allowed for their differentiation. The novel technique allows more rapid sample preparation for chromatographic detection of smokeless powders.