Feasibility of a New Method for Identification and Discrimination of Gunshot Residues by Total Reflection X-Ray Fluorescence and Principal Component Analysis

Abstract

This study aims at identifying and discriminating gunshot residue (GSR) from conventional ammunition of six different calibers by total reflection X-ray fluorescence (TXRF) and pattern recognition by principal component analysis (PCA). GSR samples were collected from hands of volunteer shooters with swabs moistened with deionized water and were extracted with 5% v v-1 nitric acid. Aliquots were deposited on quartz disks for further determination by TXRF of the elements Al,

Elemental profiling of total gunshot residue using total reflection X‐ray fluorescence spectrometry

“…The analysis of the tGSR via TXRF revealed characteristic differential patterns in the concentrations of lead, copper, antimony, barium, iron, and zinc for the different ammunition types. These six elements were found in tGSR with statistical significance in comparison with the blank samples, visualized in Figure 4, and have been analyzed in other GSR studies [1,7,10,11,15,16]. The most prominent differences were observed in lead and copper, the two key elements that make up some bullets and most jacketing, respectively.…”

“…TXRF has previously been used to analyze gunshot residue [15,16]. One study was used to detect gunpowder residue on skin, focusing on concentrations of lead, copper, barium, iron, and zinc [15].…”

“…This research showed that those elements were good distinguishers in identifying gunshot residue with lead, copper, and barium being the most influential on the results. Another study used TXRF to differentiate between different calibers of ammunition, also from the hands of various shooters [16]. This study used TXRF to measure the concentrations of various elements to examine sample discrimination between six common calibers of ammunition.…”

“…Because TXRF is an elemental analytical technique, chemical changes do not alter elemental identities and consequently would not impact elemental identification. Additionally, these chemographic tests are not TXRF has previously been used to analyze gunshot residue [15,16]. One study was used to detect gunpowder residue on skin, focusing on concentrations of lead, copper, barium, iron, and zinc [15].…”

“…Similar to iron, the precision of the zinc data was inconsistent with RSD values ranging from just under 5% to 85%. Zinc is mostly found as part of the primer housing component [1,16], in which the backward dispersion of vaporized primer residue can also explain the variation and inconsistent RSD.…”