Trace element profiling of gunshot residues by PIXE and SEM‐EDS: a feasibility study

A feasibility study was carried out into the use of particle‐induced x‐ray emission (PIXE) on the ion microprobe for the characterisation of gunshot residues (GSR). We compare these results with the conventional technique, scanning electron microscopy with energy dispersive x‐ray spectroscopy (SEM‐EDS). Samples of gunshot residue from four different sources were collected. Individual particles of GSR were analysed by SEM‐EDS using a 30‐keV electron beam focussed to ∼10 nm, and PIXE using a 2.5‐MeV proton beam focussed to ∼4 µm. PIXE revealed trace or minor elements undetectable by SEM‐EDS, thereby strengthening the discrimination between different types of GSR.