This article reports on the authors’ use of direct analysis in real time-mass spectrometry to detect organic gunshot residues in several different matrices of interest for forensics, customs, and homeland security; it describes the authors’ research methodology and outcomes, as well as the implications of their results.
This study reports the use of direct analysis in real time-mass spectrometry (DART-MS) for the detection of organic gunshot residues (OGSR) in a variety of matrices of interest for forensics, customs, and homeland security. The collection of mass spectra at multiple in-source collision-induced dissociation (is-CID) voltages produced distinctive mass spectral signatures with varying levels of fragmentation and allowed differentiation of isomers. To test method performance, the authors analyzed a collection of 330 authentic specimens from various substrates: neat smokeless powders; spent cartridge cases; burnt particles removed from clothing via carbon stubs or with tweezers; and hand samples from non-shooters and from shooters. The authors further analyzed a subset of hand specimens by liquid chromatography-tandem mass spectrometry (LC-MS/MS) for confirmation and comparison. They monitored seven types of ammunition from five manufacturers and two calibers for OGSR profiles with similar compositions observed for paired sets (e.g., unburnt smokeless powder and the respective residues on spent cartridges, clothing, and hands). The authors observed no false positives across all datasets. A 100 percent true positive rate (TPR) was observed for all substrates except the shooters' hands. Depending on the ammunition type and classification criteria, the shooters' hands exhibited a TPR ranging from 19 to 73 percent. The results show that DART-MS is feasible and versatile for fast screening of OGSR across various substrates but may benefit from alternative approaches to improve detection at trace levels. Publisher Abstract Provided
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