Forensic glass analysis by ICP-MS: a multi-element assessment of discriminating power via analysis of variance and pairwise comparisons

Abstract

Ti) to use for discrimination among the glass samples. This multi-element discrimination showed a significant improvement in the discrimination statistics over using only refractive index (RI) measurements. Oak Ridge National Laboratory (ORNL) recently analyzed fragments from 76 of the original side window fragments using inductively coupled plasma mass spectrometry (ICP-MS). The ICP-MS analyses measured 45 elements using a hierarchical sampling scheme to estimate variances due to sampled population (V P ), variance due to sample dissolution and within sample heterogeneity (V D ), and variance due to replicate measurements (V M ). The between-to-within ratio [B/W ~VP /(V D 1 V M )] afforded a measure of the variance within the population to that in the analytical measurement, providing a first approximation of the discriminating power of each element. Florida International University updated the RI measurements on 72 available glass fragments. These RI measurements along with ICP-AES and ICP-MS elemental analyses were used for pairwise comparisons of all possible pairs of the 72 glasses that had a complete set of measurements. The pairwise comparisons used Tukey's HSD method to compare RI and element-by-element discrimination potential of ICP-AES and ICP-MS for analyzing glass in forensic casework.

Forensic Discrimination of Sheet Glass Exposed to High Temperature by the Determination of Trace Impurities Using ICP-MS

“…A number of studies have reported that comparisons of elemental compositions are useful for the forensic discrimination of glass fragments, 5,6,8,9,12,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] and it is not pointed out again in this paper. What should be emphasized here is that a good correlation was observed in the elemental profiles between the non-heated and heated fragments in any of the 5 glasses.…”

“…[1][2][3][4][5][6] The forensic glass comparison mentioned above has been conducted by measuring the refractive index (RI) [5][6][7][8][9][10][11][12][13][14] and conducting an analysis of the elemental compositions using procedures such as X-ray fluorescence spectrometry (XRF), 6,8,12,[15][16][17][18][19][20][21][22] inductively coupled plasma atomic emission spectrometry (ICP-AES) 8,15,[23][24][25] and mass spectrometry (ICP-MS). 5,6,9,12,18,[26][27][28][29] An RI measurement can be applied to a glass fragment smaller than 0.1 mm in a maximum width without its destruction. This method has another advantage of simple sample preparation and short measurement time.…”

Forensic Chemistry Education

“…Elemental analysis of glass is now commonly performed with inductively coupled plasma (ICP) optical emission spectrometry, ICPMS, X-ray fluorescence, or scanning electron microscopy; ICP provides better detection limits and discrimination power than other elemental techniques (25)(26)(27) ). An ICP mass spectrometer and a laser ablation (LA) sample introduction system used together offer the advantages of minimum removal of sample by LA and the excellent sensitivity and precision of ICPMS (28)(29)(30).…”

Application of Total Reflection X-ray Fluorescence Spectrometry to Small Glass Fragments

“…Various techniques of elemental analysis have been proposed for discrimination of glass samples, such as XRF, [2][3][4][5] EPMA, 6 AAS, 7 NAA, 8 ICP-AES, 2,9,10 ICP-MS, [11][12][13] and LA-ICP-MS. 14,15 For discrimination of glass, ICP-MS can widely be used to perform multielemental analysis with higher sensitivity than other techniques. However, it is difficult to apply ICP-MS for analysis of a small glass fragment, since glass samples found at crime scenes are often extremely small.…”