Principal component analysis for the forensic discrimination of black inkjet inks based on the Vis–NIR fibre optics reflection spectra. (December 2015)

• Record Type: Journal Article
• Authors: Gál, Lukáš; Oravec, Michal; Gemeiner, Pavol; Čeppan, Michal
• Is Part Of: Forensic science international. Volume 257(2015)
• Page Start: 285
• Page End: 292
• Publication Date: 2015-12
• Subjects: Forensic document examination -- Principal component analysis -- Vis–NIR spectrophotometry -- Inkjet ink; Medical jurisprudence -- Periodicals; Chemistry, Forensic -- Periodicals; Forensic Medicine -- Periodicals; Médecine légale -- Périodiques; Chimie légale -- Périodiques; Gerechtelijke geneeskunde; Gerechtelijke chemie; Gerechtelijke psychiatrie; Chemistry, Forensic; Medical jurisprudence; Electronic journals; Periodicals; Electronic journals; 614.1
• DOI: 10.1016/j.forsciint.2015.09.011
• Languages: English
• ISSNs: 0379-0738

Abstract

Graphical abstract: Highlights: FORS spectra of inkjet prints were obtained in a complete nondestructive way. Portable Vis–NIR spectrometer, allowing evidence of alteration to be uncovered. PCA was able differentiate samples into the groups. Inkjet inks with carbon black were separated from the other. Validation proved the applicability of the method for differentiation of printer. Abstract: Nineteen black inkjet inks of six different brands were examined by fibre optics reflection spectroscopy in Visible and Near Infrared Region (Vis–NIR FORS) directly on paper with a view to achieving good resolution between them. These different inks were tested on nineteen different inkjet printers from three brands. Samples were obtained from prints by reflection probe. Processed reflection spectra in the range 500–1000 nm were used as samples in principal component analysis. Variability between spectra of the same ink obtained from different prints, as well as between spectra of square areas and lines was examined. For both spectra obtained from square areas and lines reference, Principal Component Analysis (PCA) models were created. According to these models, the inkjet inks were divided into clusters. PCA method is able to separate inks containing carbon black as main colorant from the other inks using other colorants. Some spectra were recorded from another piece of printer and used as validation samples. Spectra of validation samples were projected onto reference PCA models. According to position of validation samples in score plots it can be concluded that PCA based on Vis–NIR FORS can reliably differentiate inkjet inks which are included in the reference database. The presented method appears to be a suitable tool for forensic examination of questioned documents containing inkjet inks. Inkjet inks spectra were obtained without extraction or cutting sample with possibility to measure out of the laboratory