Standard Test Method for Forensic Comparison of Glass Using Micro X-ray Fluorescence (µ-XRF) Spectrometry

Importancia y uso:

4.1 µ-XRF provides a means of simultaneously detecting major, minor, and trace elemental constituents in small glass fragments such as those frequently examined in forensic casework. It can be used at any point in the analytical scheme without concern for changing sample shape or sample properties, such as RI, due to its nondestructive nature.

4.2 Limits of detection (LOD) (see Section 12) are dependent on several factors, including instrument configuration and operating parameters, sample thickness, and atomic number of the individual elements. Typical LODs range from parts per million (µgg^-1) to percent (%). (See Section 11.)

4.3 µ-XRF provides simultaneous qualitative analysis for elements having an atomic number of eleven and greater. This multi-element capability permits detection of elements typically present in glass such as sodium (Na), magnesium (Mg), silicon (Si), aluminum (Al), calcium (Ca), potassium (K), iron (Fe), titanium (Ti), strontium (Sr), and zirconium (Zr), as well as other elements that are present in some glass (for example, molybdenum (Mo), selenium (Se), or erbium (Er)), without the need for a predetermined elemental menu.

4.4 µ-XRF comparison of glass fragments provides additional discriminating power beyond what can be achieved by comparison of other physical and optical properties of the glass fragments (for example, RI, glass thickness).

4.5 The method precision is established by each Forensic Science Service Provider (FSSP) for the specific conditions and instrumentation in use.

4.6 When using small fragments having varying surface geometries and thicknesses, precision deteriorates due to take-off-angle and critical depth effects. Flat fragments with thickness greater than 1.5 mm do not suffer from these constraints, but are not always available as questioned samples received in casework. As a consequence of the deterioration in precision for small fragments and the lack of appropriate calibration standards, µ-XRF analysis incorporates element intensity ratios.

4.7 Appropriate sampling techniques described in this method account for natural heterogeneity of the material, varying surface geometries, and potential critical depth effects.

Subcomité:

E30.15

Referida por:

E3462-25, E2927-23, E3295-23

Volúmen:

14.02

Número ICS:

07.140 (Forensic science), 81.040.10 (Raw materials and raw glass)

Palabras clave:

elemental analysis; forensic science; glass; glass comparisons; micro X-ray fluorescence spectrometry;