The analysis of glass from portable electronic devices and glass accessories using µ-XRF for forensic investigations

Oriana Ovide; Ruthmara Corzo; Tatiana Trejos

doi:10.1016/j.forsciint.2022.111550

The analysis of glass from portable electronic devices and glass accessories using µ-XRF for forensic investigations

Forensic Sci Int. 2023 Feb:343:111550. doi: 10.1016/j.forsciint.2022.111550. Epub 2023 Jan 5.

Authors

Oriana Ovide¹, Ruthmara Corzo², Tatiana Trejos³

Affiliations

¹ West Virginia University, Department of Forensic and Investigative Sciences, Morgantown, WV 26506, the United States of America.
² National Institute of Standards and Technology, Materials Measurement Science Division, Gaithersburg, MD 20899, the United States of America.
³ West Virginia University, Department of Forensic and Investigative Sciences, Morgantown, WV 26506, the United States of America. Electronic address: tatiana.trejos@mail.wvu.edu.

PMID: 36623406
DOI: 10.1016/j.forsciint.2022.111550

Abstract

In this study, glass from 30 different portable electronic devices (PED) screens, 15 screen protectors (SP), and 3 brands of liquid glass (LG) were analyzed using a µ-XRF instrument equipped with two silicon drift detectors (SDD). Additional analysis of six fragments, all originating from the same PED and SP screen, assessed the elemental homogeneity within a single glass source. Examinations of the 30 PEDs and the majority of the SP screens revealed spectra with low sodium and high potassium, which is likely due to the ion exchange process at the surface during the glass manufacturing process. The absence of calcium in the XRF spectra was also characteristic of PED formulations. Initial spectral overlay examinations classified the PED and SP samples into major groups based on their distinctive elemental profiles (5 PED groups, 4 SP groups). Further discrimination of within-group samples was possible when considering reproducible differences in signal intensities (discrimination 98.4 % PED, 98.1 % SP). Additionally, a 3 s (3 % Relative Standard Deviation, RSD) comparison criterion produced the lowest false exclusion rates among same-source fragments (3.3 % PED, 0.8 % SP) while maintaining a high discrimination power among different-source fragments (98.4 % PED, 100 % SP). Same source PED and SP samples resulted in low variability within most elements examined (< 8 % RSD), except for potassium. An experimental threshold established from the quantitative metric of spectral similarity, spectral contrast angle (SCA) ratio of same-source and different-source datasets, produced false exclusion and false inclusion rates of 4 % or 0.95 % for PED and SP fragments, respectively. Spectra of just the liquid glass residues indicated some major elements present but the effect of these elements in PED fragments treated with liquid glass was not significant. This study provides a preliminary understanding of the elemental composition of modern PED glasses and their accessories and the discrimination capability of µ-XRF for forensic comparisons.

Keywords: Aluminosilicate glass; Liquid glass; Portable electronic devices; Spectral contrast angle (SCA) ratios; µ-XRF.