ASTM E2927-16e1 pdf free download.Standard Test Method for Determination of Trace Elements in Soda-Lime Glass Samples Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry for Forensic Comparisons.
One objective of a forensic glass examination is to compare glass samples to determine if they may be discriminated using their physical, optical or chemical properties (for example, color, refractive index (RI), density, elemental composition). If the samples are distinguishable in any of these observed and measured properties, it may be concluded that they did not originate from the same source of broken glass. If the samples are indistinguishable in all of these observed and measured properties, the possibility that they originated from the same source of glass may not be eliminated. The use of an elemental analysis method such as laser ablation inductively coupled plasma mass spectrometry yields high discrimination among sources of glass.
ASTM E2927-16e1 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 glass fragments usually do not require sample preparation prior to the LA-ICP-MS analysis. However, they may be washed with solvents or pre-ablated if necessary.
The glass fragment is placed inside an ablation chamber and a laser beam is focused on the surface of the sample. When the ablation is started, the interaction between the pulsed laser and the sample surface produces a cloud of very small particles, which are transported from the ablation cell by a carrier gas into the ICP-MS for analysis.
An ICP-MS is used to quantify the elements of interest.
Quantitative analysis is accomplished using well-characterized glass standards whose major elemental composition is similar to the material to be analyzed.
A comparison between the reported elemental compositions of the known and recovered glass fragments may result in a decision on whether the samples are distinguishable by elemental composition or indistinguishable by elemental composition.
Commercial laser ablation units are enclosed type I lasers. However, laser systems typically used for analysis of glass generate high energy radiation that may pose serious risks to eye safety if exposed to the eye. Interlocks shall not be bypassed or disconnected.
Limits of detection and limits of quantitation were determined by laboratory analysis procedures prior to publication of this test method. Limits of detection (LOD) were determined for each element by measuring procedure blanks on two non-consecutive days using a quadrupole ICP-MS and a Nd-YAG 213-nm laser. Each day, the mean and standard deviation of replicate measurements were calculated. LODs were computed as 3 times the standard deviation. LOQs were computed as 10 times the standard deviation. Normalized intensities were converted to concentrations using the calibration data for each element for that day. Values reported in Appendix X1 are two-day averages.
Keywords:forensic science; glass comparisons; glass measurement; trace elemental analysis; laser ablation; inductively coupled plasma mass spectrometry; LA-ICP-MS