Application of different standard loading approaches during solid phase microextraction for forensic analysis of single particle smokeless powders

Abstract

The technique of solid phase microextraction incorporates sampling, isolation and enrichment into a single sample preparation step, making it useful for forensic applications such as the analysis of gunpowder present at trace levels. In this study, three standard loading approaches for the analysis of compounds in smokeless powder – namely the direct headspace extraction of pure standard compounds, the syringe-fibre transfer and the in-vial standard loading approaches – were evaluated. The in-vial standard loading approach was found to be the most suitable method for both the standard curve preparation and sample analysis. Method specificity, linearity, precision, accuracy, recovery, method detection limit and the limit of quantitation were investigated for its intended purpose through the examination of common stabilisers and additives in smokeless powders, namely naphthalene, 2,6-dinitrotoluene, 2,4-dinitrotoluene, diphenylamine, N,N-diphenylformamide, methyl centralite and ethyl centralite by the gas chromatography-flame ionisation detection technique. Examination of four ammunition types of 9 mm calibre enabled their differentiation among the respective smokeless powder samples through comparison of the abundance of selected compounds.