Forensic laboratories routinely conduct analysis of glass fragments to determine whether there is an association between a fragment(s) recovered from a crime scene or from a suspect to a particular source of origin. The physical and optical (refractive index) properties of the fragments are compared and, if a "match" between two or more fragments is found, further elemental analysis can be performed to enhance the strength of the association. A range of spectroscopic techniques has been used for elemental analysis of this kind of evidence, including inductively coupled plasma mass spectrometry (ICP-MS). Because of its excellent sensitivity, precision, and accuracy, several studies have found that ICP-MS methods (dissolution and laser-ablation) provide the best discrimination between glass fragments originating from different sources. Nevertheless, standard unit-resolution ICP-MS instruments suffer from polyatomic interferences including 40Ar16O+, 40Ar16O1H+, and refractory oxide 40Ca16O+ that compromise measurements of trace levels of Fe56+ and Fe57+, for example. This is a drawback in the analysis of glass fragments, because iron has been previously identified as a good discriminating element. Currently, several techniques are available that enable reduction of such interferences; however, there are no data that compare detection limits of iron in glass using those techniques. In addressing this issue, the current study conducted analyses that used conventional acid-digestion and laser-ablation methods. For laser-ablation analyses, carrier gases were compared to assess the effect on detection limits in the detection of iron isotopes. Iron polyatomic interferences were reduced or resolved by using a dynamic reaction cell and high-resolution ICP-MS. MDLs as low as 0.03 g g1 and 0.14 g g1 were achieved in laser-ablation and solution-based analyses, respectively. Use of helium as carrier gas improved detection limits for both iron isotopes in medium-resolution HR-SF-ICP-MS and in DRC-ICP-MS. 47 references (publisher abstract modified)
Comparison of High-Resolution and Dynamic Reaction Cell ICP-MS Capabilities for Forensic Analysis of Iron in Glass
NCJ Number
255280
Journal
Analytical and Bioanalytical Chemistry Volume: 392 Issue: 4 Dated: 2008 Pages: 663-672
Date Published
2008
Length
10 pages
Annotation
This article reports on the findings and methodology of a study that compared the analytical performance of high-resolution sector field inductively coupled plasma mass spectrometry (HR-SF-ICP-MS) and quadrupole ICP-MS equipped with a dynamic reaction cell (DRC-ICP-MS) for the detection of iron in glass, in terms of accuracy, precision, and method detection limits (MDLs).
Abstract
Date Published: January 1, 2008