5.1 This test method is useful for the determination of elemental concentrations in the range of approximately 0.1 µgg^-1 to 10 percent (%) (See Table X1.1) in soda-lime glass samples (7 and 8). A standard test method can aid in the interchange of data between laboratories and in the creation and use of glass databases.

5.2 The determination of elemental concentrations in glass provides high discriminating value in the forensic comparison of glass fragments.

5.3 This test method produces minimal destruction of the sample. Microscopic craters of 50 µm to 100 µm in diameter by 80 µm to 150 µm deep are left in the glass fragment after analysis. The mass removed per replicate is approximately 0.4 µg to 3 µg (6).

5.4 Appropriate sampling techniques shall be used to account for natural heterogeneity of the materials at a microscopic scale.

5.5 The precision, bias, and limits of detection of the method (for each element measured) shall be established during validation of the method. The measurement uncertainty of any concentration value used for a comparison shall be recorded with the concentration.

5.6 Acid digestion of glass followed by either Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) or Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) can also be used for trace elemental analysis of glass, and offer similar detection levels and the ability for quantitative analysis. However, these methods are destructive, and require larger sample sizes and more sample preparation (Test Method E2330).

5.7 Micro X-Ray Fluorescence (µ-XRF) uses comparable sample sizes to those used for LA-ICP-MS with the advantage of being non-destructive of the sample. Some of the drawbacks of µ-XRF include lower sensitivity and precision, and longer analysis time (Test Method E2926).

5.8 Scanning Electron Microscopy with Energy Dispersive Spectrometry (SEM-EDS) is also available for elemental analysis, but it is of limited use for forensic glass source discrimination due to poor detection limits for higher atomic number elements present in glass at trace concentration levels. However, distinguishing between sources having similar RIs and densities is sometimes possible.

1.1 This test method covers a procedure for the quantitative elemental analysis of the following seventeen elements: lithium (Li), magnesium (Mg), aluminum (Al), potassium (K), calcium (Ca), iron (Fe), titanium (Ti), manganese (Mn), rubidium (Rb), strontium (Sr), zirconium (Zr), barium (Ba), lanthanum (La), cerium (Ce), neodymium (Nd), hafnium (Hf) and lead (Pb) through the use of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for the forensic comparison of glass fragments. The potential of these elements to provide the best discrimination among different sources of soda-lime glasses has been published elsewhere (1-5).2 Silicon (Si) is also monitored for use as a normalization standard. Additional elements may be added as needed, for example, tin (Sn) can be used to monitor the orientation of float glass fragments.

1.2 The method only consumes approximately 0.4 µg to 3 µg of glass per replicate and is suitable for the analysis of full thickness samples as well as irregularly shaped fragments as small as 0.1 mm by 0.1 mm by 0.2 mm (6) in dimension. The concentrations of the elements listed above range from the low parts per million (µgg^-1) to percent (%) levels in soda-lime glass, the most common type encountered in forensic cases. This standard method can be applied for the quantitative analysis of other glass types; however, some modifications in the reference standard glasses and the element menu may be required.

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

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

1.5 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.

1.6 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.