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.

1.1 This test method is for the determination and comparison of major, minor, and trace elements present in glass fragments through the use of µ-XRF analysis.

1.2 This test method covers the application of µ-XRF using collimator, mono- and poly-capillary optics, and an energy dispersive X-ray detector (EDS).

1.3 This test method is intended for comparisons in which at least one of the compared fragments is a glass type supported by published research regarding elemental heterogeneity (for example, soda-lime glass). This standard method can be applied to other glass types; however, scientifically supported method modifications and method validations might be appropriate.

1.4 This test method includes method requirements, method recommendations, and informational guidance.

1.5 This standard is intended for use by competent forensic science practitioners (FSPs) with the requisite formal education, discipline-specific training (refer to Practice E2917), and demonstrated proficiency to perform forensic casework.

1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.