ANALYSIS OF LEAD-FREE AMMUNITION BY SCANNING ELECTRON MICROSCOPY USING ENERGY DISPERSIVE X-RAY SPECTROSCOPY AND DISCRIMINATION OF SAMPLES USING MULTIVARIATE STATISTICAL METHODSBySeth R. HoggSix commonly available brands of non-toxic, 9 mm ammunition as well as the most common brand of road safety flare utilized in the United States were purchased. Five rounds from each box were fired as purchased while five were disassembled allowing firing of only primer components in the presence of three conductive carbon tabs positioned near the weapon muzzle, permitting capture of gunshot residue (GSR). Road flares were burned in the presence of two conductive tabs positioned above the flare to capture any ejected particles during the combustion process.A carbon tab was analyzed from each of the resulting 61 samples using a scanning electron microscope (SEM). Particles visually consistent with the morphology of GSR were located on the tabs designating the area as a region of interest and all particles within view were analyzed by EDS. Searching of each sample finished after 30 regions of interest were identified. Maximum peak height normalization was applied to the resulting spectra prior to statistical analysis. The pretreated data were then analyzed using principal components analysis (PCA) to investigate association of ammunition by manufacturer, based on the element profiles generated. Then, the association of samples from whole bullets to those from primers only, and the differentiation of actual GSR from a ubiquitous road flare were also investigated using PCA.
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