Microtrace Article: Glass Analysis by X-ray Fluorescence Spectrometry

Micro X-ray Fluorescence Spectrometry (µXRF) is a well-established technique for the elemental analysis of glass in forensic casework. The standard test method for the forensic analysis of glass using µXRF (ASTM E2926) provides recommendations for the number of replicate measurements that should be collected to characterize a known source and the criteria for the comparison between the known and questioned samples. However, these recommendations were based on interlaboratory data collected using µXRF instrumentation equipped with traditional lithium-doped silicon (SiLi) detectors. This interlaboratory study aimed to evaluate the performance of modern µXRF systems equipped with silicon drift detectors (SDDs) for the forensic comparison of glass. While the SDD-µXRF instruments resulted in improved precision and detection limits (1.4 µg·g⁻¹–1386 µg·g⁻¹) and excellent discrimination (>99 %) of different-source samples, the false exclusion rates for same-source samples were relatively high (>20 %). Two methods were evaluated to reduce the high false exclusion rates: increasing the number of fragments collected for the known source and modifying the recommended comparison criteria. To reduce the false exclusion rate to 5 % or less, a minimum of five known fragments were needed. Alternatively, modifying the recommended comparison criterion reduced the false exclusion rate from 23 % to 2 %, while maintaining low false inclusions (<1%). The findings in this study demonstrate the improved sensitivity and precision observed in glass measurements acquired with µXRF-SDD systems. However, these systems may require adjustments to sampling and the comparison criteria to minimize potential error rates in the forensic comparison of glass fragments.

Forensic Chemistry

Forensic Chemistry publishes high quality manuscripts focusing on the theory, research and application of any chemical science to forensic analysis. The scope of the journal includes fundamental advancements that result in a better understanding of the evidentiary significance derived from the physical and chemical analysis of materials. The scope of Forensic Chemistry also includes the application and or development of any molecular and atomic spectrochemical technique, electrochemical techniques, sensors, surface characterization techniques, mass spectrometry, nuclear magnetic resonance, chemometrics and statistics, and separation sciences (e.g. chromatography) that provide insight into the forensic analysis of materials.

Evidential topics of interest to the journal include, but are not limited to, fingerprint analysis, drug analysis, ignitable liquid residue analysis, explosives detection and analysis, the characterization and comparison of trace evidence (glass, fibers, paints and polymers, tapes, soils and other materials), ink and paper analysis, gunshot residue analysis, synthetic pathways for drugs, toxicology and the analysis and chemistry associated with the components of fingermarks. The journal is particularly interested in receiving manuscripts that report advances in the forensic interpretation of chemical evidence.