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XIV h International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017 176 T1: P–43 The use of UV/VIS and FTIR spectrometry in differentiation samples of degraded papers with application of PCA method for forensic purposes Janina Zięba-Palus 1 , Beata Trzcińska 1 , Rafał Kowalski 1 , Aleksandra Wesełucha-Birczyńska 2 , and Paulina Moskal 2 1 Institute of Forensic Research, Kraków, Poland, e-mail: jzieba@ies.krakow.pl 2 Faculty of Chemistry, Jagiellonian University, Kraków, Poland The subject of forensic examination is often paper being the basis of bogus or in other manner fraudulently alternated documents. Paper owes its properties to cellulose – a structural biopolymer. Its properties are highly dependent on the interactions between and within the cellulose chains mainly regarded to inter-and intramolecular hydrogen bonds. During paper degradation the degree of polymerization of cellulose chain changes. Cellulose degradation should be regarded in terms of mixed oxidative and hydrolytic mechanisms. Spectroscopic methods are of major importance in paper characterization. Vibrational spectroscopy has already been widely applied to resolve cellulose structure, crystalline phases and hydrogen bonds network [1-4]. The aim of the present research was to analyse degraded papers by spectroscopic techniques and to evaluate the possibility of differentiation between them. Six paper samples were artificially aged in a climatic chamber under 100% relative humidity in air at 90°C for various periods up to 35 days. The samples were also aged in normal conditions, i.e. in room temperature in darkness and in sun light for various periods up 24 months. The conditioned samples differing in ageing time were subjected to further analyses. FTIR spectra were collected on IS50 Thermo Scientific spectrometer at an optical resolution of 4 cm-1 using ATR technique. VIS spectra were recorded using spectrophotometer 20/20 PV TM CRAIC in the range 200–800 nm. It was observed that the paper samples differ slightly in the range 1000–1120, 2860–2950 and 1300–1380 cm –1 in infrared in the function of time. The differences were also found in UV/VIS spectra and concerned intensity of ca. 280 and 350 nm bands. 2D correlation spectroscopy clearly differentiated impact of aging process on the tested cards. Fig. 1. 2D correlation asynchronous map. The asynchronous maps show different cross-peaks patterns +(289, 359), -(354, 428), -(272, 427); +(311, 422), +(293, 319), +(281, 317), -(316, 354); +(257, 385), +(233, 383) and -(343, 411), -(293, 405) for the 1st, 2nd, 4th and 5th card respectively. So, it was possible to differentiate between examined degraded paper samples. Keywords: paper; infrared spectroscopy; UV-VIS spectroscopy References [1] M. Manso, M.L. Carvalho, Spectrochim. Acta B 64 (2009) 482. [2] M. Bicchieri, A. Sodo, G. Piantanida, C. Coluzza, J. Raman Spectroscopy 37 (2006) 1186. [3] M. Ali, A.M. Emsley, H. Herman, R.J. Heywood, Polymer 42 (2001) 2893. [4] J. Zięba-Palus, A. Wesełucha-Birczyńska, B. Trzcińska, R. Kowalski, P. Moskal, J. Mol. Struct. 1140 (2017) 154. XIV h International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017 177 T1: P–44 The influence of the type of substrate on the possibility of spray paint identification for forensic purposes Rafał Kowalski 1 , and Janina Zięba-Palus 1 1 Institute of Forensic Research, Krakow, Poland, e-mail: jzieba@ies.krakow.pl Graffiti or other daubs made by the use of spray paints destroy elevation of many buildings and are often a subject of forensic examinations [1–4]. Sometimes spray paints are used to destroy traces left by perpetrator on the crime scene. The layer of paint, which creates an inscription, smudge or a drawing, is thin and difficult to be separated from the base. Moreover, the small droplets of paint are also left on the clothing of the perpetrator. They point at his presence on crime scene. The aim of this paper was to apply infrared spectrometry (IR) and Raman spectroscopy in examination of spray paints for forensic purposes. Model examinations using spectroscopic methods (FTIR, Raman) were performed for the identification of spray paints on different substrates (glass, paper, fabrics). Seven red spray paints, available on the Polish market were placed on the surface of glass plate, paper and fabrics (cotton, polyamide, polyester). The IR spectra were recorded on Nicolet iN10 spectrometer (Thermo Scientific) with Omnic Picta program, in transmission mode, in the range 600–4000 cm –1 . Raman spectra were obtained by means of InVia Raman Microscope, (Renishaw UK), lasers: 514, 633 and 785 nm, spectra recorded in the range 200–2000 cm –1 . Raman shift [cm -1 ] Wavenumber [cm -1 ] Fig. 1. Raman (a) and infrared (b) spectra of spray paint placed on different substrates. It was found that it is possible to differentiate spray paints using both IR and Raman spectroscopy. FT-IR technique allows to identify the main polymers and fillers in spite of the influence of the substrate. Raman spectroscopy provides information about pigment composition but sometimes results are influenced by inhomogeneity in pigment distribution in paint. Keywords: spray paint; infrared spectroscopy; Raman spectroscopy References [1] J. Zięba-Palus, J. Mol. Stuct. 744–747 (2005) 229. [2] J. Milczarek, J. Zięba-Palus, Anal. Appl. Pyrol. 86 (2009) 252. [3] C. Muehlethaler, G. Massonnet, P. Buzzini, Forensic Sci. Int. 237 (2014) 78. [4] C. Muehlethaler, G. Massonnet, P. Esseiva, Forensic Sci. Int. 244 (2014) 170. Yüklə 20,03 Mb. Dostları ilə paylaş:
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