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This paper presents a novel approach in non-destructive analysis of inkjet-printed documents. Our method is based on the combination of molecular spectroscopy in the Near Infrared Region (NIR) and a chemometric method - principal component analysis (PCA). The aim of this work was to prepare spectral data for the analysis of the interrelationships between 19 samples consisting of the same type of office paper on which black squares were full printed in black ink only. The spectra were obtained separately using the Ocean Optics System in two spectral regions, i.e., overtones: 1000-1600 nm and combination bands: 1600-2300 nm, with the paper base. Experimental results confirmed the high reliability of the proposed approach despite the sparse dataset. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This work presents an investigation of 98 black-and-white historical photographs of three type of binders (albumen, gelatin, and collodion). The work is aimed to differentiate photographic processes using an effective approach of near-infrared (NIR) spectroscopy combined with the multivariate statistical method of principal component analysis (PCA). Methods, e.g., detrending and normalization, processed the dataset of 882 spectra. The PCA results were compared with the method of attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy. This comparison indicates the chemometric approach as a very perspective to examine historical photographs in a fast and non-destructive fashion. • Investigation of 98 black-and-white historical photographs of three binder types • ATR-FTIR, NIR, and PCA to non-destructive and easy identifying the photographs • The NIR spectra preprocessing for the PCA method to split the sample into the groups • Classification in the context of comparison with the established method of ATR-FTIR [ABSTRACT FROM AUTHOR]