ASTM E2926-17 PDF

Overview

ASTM E2926-17 is the Standard Test Method for Forensic Comparison of Glass Using Micro X-ray Fluorescence (μ-XRF) Spectrometry, established by ASTM International. This standard outlines a nondestructive analytical approach for comparing glass fragments through the simultaneous detection of major, minor, and trace elements using μ-XRF. Commonly applied in forensic science, this method enhances discrimination power in glass fragment comparison, supporting investigations and legal proceedings.

Key Topics

• μ-XRF Analysis: Employs capillary optics and energy dispersive X-ray detectors to analyze elemental composition in glass fragments without altering sample properties or shape.
• Elemental Detection: Capable of detecting elements with atomic number 11 or higher, including magnesium (Mg), silicon (Si), aluminum (Al), calcium (Ca), potassium (K), iron (Fe), titanium (Ti), strontium (Sr), and zirconium (Zr).
• Non-destructive Testing: Preserves the integrity and physical properties of glass evidence, allowing repeated and multi-step analyses.
• Detection Limits: Typical μ-XRF limits of detection range from parts per million (ppm) to percent, depending on instrument settings, sample thickness, and element type.
• Qualitative and Semi-Quantitative Results: Provides qualitative profiles and semi-quantitative comparisons (using elemental peak intensity ratios) between questioned and known glass samples.
• Precision and Best Practices: Emphasizes the need for laboratory-specific precision validation, appropriate sample preparation, and regular system calibration to maintain data integrity.

Applications

• Forensic Glass Comparison: Vital in crime scene investigations involving glass fragments (e.g., burglary, vandalism, traffic accidents), supporting source attribution or exclusion.
• Legal Evidence: μ-XRF data is used as robust supplementary evidence, providing higher discrimination than refractive index (RI) or density measurement alone.
• Material Science: Assists in glass quality control and source verification in manufacturing and research contexts.
• Non-invasive Sampling: Especially valuable when only small or precious specimen samples are available, as μ-XRF is entirely nondestructive.
• Database Collection: Facilitates creation and use of spectral databases for known glass types, streamlining casework comparisons and interlaboratory studies.

Related Standards

• ASTM E2330: Standard Test Method for Determination of Concentrations of Elements in Glass Samples Using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for Forensic Comparisons. Provides destructive, quantitative trace analysis as a complement to μ-XRF.
• ASTM E177: Practice for Use of the Terms Precision and Bias in ASTM Test Methods. Cited for establishing test precision and repeatability in μ-XRF applications.
• ICP-OES and LA-ICP-MS Methods: Offer alternative techniques, including destructive and non-destructive options, depending on analytical requirements.
• Standard Reference Materials (SRM): Use of NIST SRM 1831 and other certified reference materials ensures calibration reliability and data comparability.

Practical Value

The adoption of ASTM E2926-17 improves forensic laboratories’ capability to perform objective, sensitive, and repeatable comparisons of glass evidence. By following standardized procedures, forensic practitioners ensure consistent generation of high-quality analytical data that withstands scrutiny in legal and scientific forums. This standard is critical for enhancing evidential value in glass analysis, upholding best practices in forensic science, and supporting reliable outcomes in both investigative and quality control settings.

Keywords: forensic glass comparison, micro X-ray fluorescence, μ-XRF spectrometry, elemental analysis, ASTM E2926-17, forensic science, nondestructive testing.