Evaluation of the Evidential Value of the Elemental Composition of Glass, Ink and Paper by Laser-Based Micro-Spectrochemical Methods

Abstract

DEDICATIONThis dissertation is dedicated to my family, especially to my husband and my mom who are my day-to-day inspiration. I have learned from you both how to be perseverant and keep believing in our dreams. I also dedicate this work to my lovely kids: Montserrat and Anthony, being your mom has been God's greatest gift and privilege. In the first part of this study, the analytical performance of LIBS and LA-ICP-MS methods was evaluated for paper, writing inks and printing inks. A total of 350 ink specimens were examined including black and blue gel inks, ballpoint inks, inkjets and toners originating from several manufacturing sources and/or batches. The paper collection set consisted of over 200 paper specimens originating from 20 different paper sources produced by 10 different plants.Micro-homogeneity studies show smaller variation of elemental compositions within a single source (i.e., sheet, pen or cartridge) than the observed variation between different sources (i.e., brands, types, batches). Significant and detectable differences in the elemental profile of the inks and paper were observed between samples originating from different sources (discrimination of 87 -100% of samples, depending on the sample set under investigation and the method applied). These results support the use of vii elemental analysis, using LA-ICP-MS and LIBS, for the examination of documents and provide additional discrimination to the currently used techniques in document examination.In the second part of this study, a direct comparison between four analytical methods (µ-XRF, solution-ICP-MS, LA-ICP-MS and LIBS) was conducted for glass analyses using interlaboratory studies. The data provided by 21 participants were used to assess the performance of the analytical methods in associating glass samples from the same source and differentiating different sources, as well as the use of different match criteria (confidence interval (±6s, ±5s, ±4s, ±3s, ±2s), modified confidence interval, t-test (sequential univariate, p=0.05 and p=0.01), t-test with Bonferroni correction (for multivariate comparisons), range overlap, and Hotelling's T 2 tests. Error rates (Type 1 and Type 2) are reported for the use of each of these match criteria and depend on the heterogeneity of the glass sources, the repeatability between analytical measurements, and the number of elements that were measured. The study provided recommendations for analytical performance-based parameters for µ-XRF and LA-ICP-MS as well as the best performing match criteria for both analytical techniques, which can be applied now by forensic glass examiners.

Forensic Examination and Identification of Writing Inks on Documents

“…Inks and their chemical composition can be classified based on basis of pen types including liquid, aqueous, paste or powder. Other basis of classification is it's end use that includes writing and printing inks as two main classes [1,6]. Some of the inks with related substance encountered in forensic examination include ballpoint pen ink, roller ball pen ink, fiber tip pen ink, marker ink, fountain pen ink, gel pen ink, porous tip pen ink, plastic tip pen ink, pencil, rubber stamp ink, ink jet printer ink, letterpress ink, typewriter ink, and copier toner [1].…”

The scientific examination of works of art on paper

“…), бојена везива (боје и пигменти) и други адитиви (скроб, гуар гума, биоциди...) који имају улогу да побољшају физичке и хемијске особине папира. Производе се на два начина: савременом машинском производњом и ручном производњом (Краигхер- Хозо, 1991;Радосављевић, 2000;Trejos, 2018) Мастила се међусобно разликују по свом хемијском саставу, по боји и по евентуалним страним примесама до којих долази у току употребе мастила. По свом хемијском саставу мастила се деле на три основне врсте: галутинска, аналинска и хромна мастила.…”

Forensic Analysis of Laser Printed Ink by X-ray Fluorescence and Laser-Excited Plume Fluorescence

“…The inorganics were the pigments as well as the charge and magnetic controllers. They had been successfully analyzed by laser-ablation inductively coupled-plasma mass-spectrometry (LA-ICPMS), , yet two issues remained. First, the questioned documents might not fit inside the small sealed chamber .…”