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See detailAnalyse moléculaire d'encres d'impression à des fins forensiques
Heudt, Laetitia ULg

Doctoral thesis (2012)

Document examination is a forensics field focused on the analysis of a disputed document. One way to analyze a document is to focus on the composition of the ink used or the materials from which documents ... [more ▼]

Document examination is a forensics field focused on the analysis of a disputed document. One way to analyze a document is to focus on the composition of the ink used or the materials from which documents are produced. Nowadays, three major classes of inks are studied: pen inks, inkjet printer inks, and toner. If the analysis of pen inks is already well developed in the literature and in the forensic lab, the analysis of inkjet printer inks is reported only to a limited degree and is principally focused on color inks. Fraudulent-minded people use more and more inkjet printer technology to produce falsified documents. So, it is a necessity to develop an analytical method for inkjet-printed document examination. Due to the particular chemical composition of these inks, different or more complicated analytical methods could and must be reviewed. Four analytical methods are evaluated in this thesis as possible tools for the analysis of inkjet-printed documents in terms of discriminating power, chemical information quality, and nondestructive capability: Raman spectroscopy and mass spectrometry coupled with Laser Desorption Ionization (LDI), Matrix Assisted Laser Desorption Ionization (MALDI), and Desorption ElectroSpray Ionization (DESI). The results obtained from two color inkjet printer cartridges (either fresh or printed) show that Raman spectroscopy and MALDI (9-aminoacridin as matrix) are the two most powerful methods for the analysis of color inkjet inks. Both methods have the advantage to perform analysis of inks directly on paper. The complementarity of the Raman spectroscopy and the MALDI-MS techniques is demonstrated based on the analysis of 10 different inkjet cartridges. The Raman method is a nondestructive approach while MALDI mass spectrometry has a better discrimination power and can also lead to information about some ink additives and paper composition. If it is necessary to determine the spatial distribution of one compound, then molecular imaging can be performed using Raman and (MA)LDI mass spectrometry. These techniques have been used successfully on a banknote or a stamp. Black inks are also under investigation in this work. The discrimination of black inkjet-printed documents is more difficult because of the common use of carbon black as the principal black pigment. LDI mass spectra recorded on black-printed inks give polyethylene glycol (PEG) peaks that are characteristics of a particular brand. Moreover, unknown characteristic peaks are detected in the low mass range of these spectra, giving additional information for discrimination of black inks. A software has been developed for a rapid and objective comparison of the low mass range of these positive mode LDI spectra. [less ▲]

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See detailRaman spectroscopy and laser desorption mass spectrometry for minimal destructive forensic analysis of black and color inkjet printed documents
Heudt, Laetitia ULg; Debois, Delphine ULg; Zimmerman, Tyler ULg et al

in Forensic Science International (2012), 219

Inkjet ink analysis is the best way to discriminate between printed documents, or even though more difficult, to connect an inkjet printed document with a brand or model of printers. Raman spectroscopy ... [more ▼]

Inkjet ink analysis is the best way to discriminate between printed documents, or even though more difficult, to connect an inkjet printed document with a brand or model of printers. Raman spectroscopy and laser desorption mass spectrometry (LDMS) have been demonstrated as powerful tools for dyes and pigments analysis, which are ink components. The aim of this work is to evaluate the aforementioned techniques for inkjet inks analysis in terms of discriminating power, information quality, and nondestructive capability. So, we investigated 10 different inkjet ink cartridges (primary colors and black), 7 from the HP manufacturer and one each from Epson, Canon and Lexmark. This paper demonstrates the capabilities of three methods: Raman spectroscopy, LDMS and MALDI-MS. Raman spectroscopy, as it is preferable to try the nondestructive approach first, is successfully adapted to the analysis of color printed documents in most cases. For analysis of color inkjet inks by LDMS, we show that a MALDI matrix (9- aminoacridine, 9AA) is needed to desorb and to ionize dyes from most inkjet inks (except Epson inks). Therefore, a method was developed to apply the 9AA MALDI matrix directly onto the piece of paper while avoiding analyte spreading. The obtained mass spectra are very discriminating and lead to information about ink additives and paper compositions. Discrimination of black inkjet printed documents is more difficult because of the common use of carbon black as the principal pigment. We show for the first time the possibility to discriminate between two black-printed documents coming from different, as well as from the same, manufacturers. Mass spectra recorded from black inks in positive ion mode LDMS detect polyethylene glycol polymers which have characteristic mass distributions and end groups. Moreover, software has been developed for rapid and objective comparison of the low mass range of these positive mode LDMS spectra which have characteristic unknown peaks. [less ▲]

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See detailDevelopment and validation of a multi-residue method for pesticide determination in honey using on-column liquid-liquid extraction and liquid chromatography-tandem mass spectrometry
Pirard, Catherine; Widart, Joëlle ULg; Nguyen, Bach Kim ULg et al

in Journal of Chromatography. A (2007), 1152(1-2), 116-123

We report on the development and validation under ISO 17025 criteria of a multi-residue confirmatory method to identify and quantify 17 widely chemically different pesticides (insecticides: Carbofuran ... [more ▼]

We report on the development and validation under ISO 17025 criteria of a multi-residue confirmatory method to identify and quantify 17 widely chemically different pesticides (insecticides: Carbofuran, Methiocarb, Pirimicarb, Dimethoate, Fipronil, Imidacloprid; herbicides: Amidosulfuron, Rimsulfuron, Atrazine, Simazine, Chloroturon, Linuron, Isoxaflutole, Metosulam; fungicides: Diethofencarb) and 2 metabolites (Methiocarb sulfoxide and 2-Hydroxytertbutylazine) in honey. This method is based on an on-column liquid liquid extraction (OCLLE) using diatomaceous earth as inert solid support and liquid chromatography (LC) coupled to mass spectrometry (MS) operating in tandem mode (MS/MS). Method specificity is ensured by checking retention time and theoretical ratio between two transitions from a single precursor ion. Linearity is demonstrated all along the range of concentration that was investigated, from 0.1 to 20 ng g(-1) raw honey, with correlation coefficients ranging from 0.921 to 0.999, depending on chemicals. Recovery rates obtained on home-made quality control samples are between 71 and 90%, well above the range defined by the EC/657/2002 document, but in the range we had fixed to ensure proper quantification, as levels found in real samples could not be corrected for recovery rates. Reproducibility is found to be between 8 and 27%. Calculated CC alpha and CC beta (0.0002-0.943 mg g(-1) for CC alpha, and 0.0002-1.232 ng g(-1) for CCP) show the good sensitivity attained by this rnulti-residue analytical method. The robustness of the method has been tested in analyzing more than 100 raw honey samples collected from different areas in Belgium, as well as some wax and bee samples, with a slightly adapted procedure. (C) 2007 Elsevier B.V. All rights reserved. [less ▲]

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