Abstract
Inorganic gunshot residue (IGSR) has certain environmental and occupational interferent-particle sources known to display similar morphologies and elemental compositions to IGSR. These interferences can make detecting and identifying IGSR particles difficult, especially when IGSR particle number concentrations are low. Here, single-particle inductively coupled plasma time-of-flight mass spectrometry (spICP-TOFMS) is used to explore the particle types measured from IGSR and three important interferent-particle sources: brake pads, fireworks, and mineral sunscreen. spICP-TOFMS offers results in as little as 2 min per sample. With spICP-TOFMS, the mass of most elements, down to the 10s of attograms, can be detected and quantified in individual particles with diameters from 10s to 100s of nm. At this size range, almost all interferent sources produce particles with elemental compositions that overlap with ASTM-defined particle compositions used for identifying leaded and lead-free IGSR. We establish probabilities for detecting IGSR-like particles from interference sources through the analysis of thousands of particles from each interference. Based on this analysis, robust sample-specific ‘characteristic’ particle types can be used to classify leaded and unleaded IGSR particles, even in the presence of interferent particles. Of the interference sources studied, particles from brake pads and fireworks are most similar to leaded IGSR; however, IGSR particles could be unequivocally classified based on detection of lead and antimony. Particles from mineral sunscreen are most similar to those from lead-free IGSR; however, lead-free IGSR particles exhibit a unique titanium-zinc-copper elemental fingerprint that is not detected in mineral sunscreen particles. Within mixtures of interference particles and IGSR, IGSR is accurately identified with limited false positives, even when the number of interference particles is over 200-times greater than that of IGSR. Our results suggest that spICP-TOFMS is a useful approach for rapid and accurate IGSR identification even in samples with high concentrations of interferent background particles.
| Original language | English |
|---|---|
| Article number | 125368 |
| Journal | Talanta |
| Volume | 268 |
| DOIs | |
| State | Published - Feb 1 2024 |
| Externally published | Yes |
Funding
The authors would like to acknowledge funding through Iowa State University faculty start-up grant. We also acknowledge ISU's Trond Forre in the Glass Shop and ISU Chemistry Machine Shop for microdroplet introduction system fabrication. We would like to acknowledge our collaboration with Dr. Trejos at West Viriginia University who provided us samples of the inorganic gunshot residue primer standards used in this study. We would also like to acknowledge Josh Wendland, who aided in collection of leaded gunshot residue samples. The authors would like to acknowledge funding through Iowa State University faculty start-up grant. We also acknowledge ISU's Trond Forre in the Glass Shop and ISU Chemistry Machine Shop for microdroplet introduction system fabrication. We would like to acknowledge our collaboration with Dr. Trejos at West Viriginia University who provided us samples of the inorganic gunshot residue primer standards used in this study. We would also like to acknowledge Josh Wendland, who aided in collection of leaded gunshot residue samples.
| Funders | Funder number |
|---|---|
| Josh Wendland | |
| Iowa State University | |
| Illinois State University |
Keywords
- Forensics
- ICP-TOFMS
- Inorganic gunshot residue
- Single particle ICP-MS