Michelle D. Sullivan, W. Pinson, Troy Eberhardt, Jonathan J Ross, Tyler W. Wood
{"title":"Deposition order and physicochemical process visualization of ink intersections using X‐ray photoelectron spectroscopy imaging for forensic analysis","authors":"Michelle D. Sullivan, W. Pinson, Troy Eberhardt, Jonathan J Ross, Tyler W. Wood","doi":"10.1002/sia.7246","DOIUrl":null,"url":null,"abstract":"The physicochemical events at ink intersections are largely understudied. Chemical imaging techniques and multivariate analyses applied to this problem thus far lack the performance characteristics to make confident conclusions about these processes. This deficiency leads to subjective and controversial deposition order determinations in forensic investigations. In this comprehensive report, 44 unique crossings involving laser toners and stamps, as well as felt‐tip, rollerball, gel, and ballpoint pen inks, were imaged with X‐ray photoelectron spectroscopy (XPS), using a 50‐μm X‐ray spot size and 100‐μm steps. The specificity and surface sensitivity of XPS enabled the objective visualization of the inks' chemistry upon deposition via spatial elemental distribution in‐situ. Signal intensity and atomic concentration were mapped for each element detected. Discrimination was possible in 100% of written and printed inks analyzed, and the relationship between the elemental concentration profile in each intersection was compared with the known sequence. Formation of ink layers, mixing, and separation of ink components by way of electrostatic forces were observed. Insights into the known complexity of ink intersection processes were revealed and highlight the need for understanding the chosen analytical technique's information depth and for complementary analyses to increase sequencing confidence. We also provide evidence that these processes invalidate the utility of principal component analysis for analyzing ink intersections. However, sequencing accuracy was 84% for all samples analyzed, and its success was highly dependent on the presence of physical features (i.e., thick coatings and embossed regions). In some intersection types, especially toners, the features exposed with XPS imaging enabled a sequencing accuracy of 100%.","PeriodicalId":22062,"journal":{"name":"Surface and Interface Analysis","volume":null,"pages":null},"PeriodicalIF":1.6000,"publicationDate":"2023-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Surface and Interface Analysis","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1002/sia.7246","RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
引用次数: 0
Abstract
The physicochemical events at ink intersections are largely understudied. Chemical imaging techniques and multivariate analyses applied to this problem thus far lack the performance characteristics to make confident conclusions about these processes. This deficiency leads to subjective and controversial deposition order determinations in forensic investigations. In this comprehensive report, 44 unique crossings involving laser toners and stamps, as well as felt‐tip, rollerball, gel, and ballpoint pen inks, were imaged with X‐ray photoelectron spectroscopy (XPS), using a 50‐μm X‐ray spot size and 100‐μm steps. The specificity and surface sensitivity of XPS enabled the objective visualization of the inks' chemistry upon deposition via spatial elemental distribution in‐situ. Signal intensity and atomic concentration were mapped for each element detected. Discrimination was possible in 100% of written and printed inks analyzed, and the relationship between the elemental concentration profile in each intersection was compared with the known sequence. Formation of ink layers, mixing, and separation of ink components by way of electrostatic forces were observed. Insights into the known complexity of ink intersection processes were revealed and highlight the need for understanding the chosen analytical technique's information depth and for complementary analyses to increase sequencing confidence. We also provide evidence that these processes invalidate the utility of principal component analysis for analyzing ink intersections. However, sequencing accuracy was 84% for all samples analyzed, and its success was highly dependent on the presence of physical features (i.e., thick coatings and embossed regions). In some intersection types, especially toners, the features exposed with XPS imaging enabled a sequencing accuracy of 100%.
期刊介绍:
Surface and Interface Analysis is devoted to the publication of papers dealing with the development and application of techniques for the characterization of surfaces, interfaces and thin films. Papers dealing with standardization and quantification are particularly welcome, and also those which deal with the application of these techniques to industrial problems. Papers dealing with the purely theoretical aspects of the technique will also be considered. Review articles will be published; prior consultation with one of the Editors is advised in these cases. Papers must clearly be of scientific value in the field and will be submitted to two independent referees. Contributions must be in English and must not have been published elsewhere, and authors must agree not to communicate the same material for publication to any other journal. Authors are invited to submit their papers for publication to John Watts (UK only), Jose Sanz (Rest of Europe), John T. Grant (all non-European countries, except Japan) or R. Shimizu (Japan only).