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Identification of paper and influence of its homogeneity in forensic investigations by ICP-AES/MS and other non-invasive spectroscopic techniques
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine.
2012 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The purpose with this thesis was to find out if ordinary office paper was homogenous throughout the sheet in context of organic and elemental content. Two different types of papers were also analyzed, paper towel and corrugated paperboard. The techniques used were NIR, FT-IR and Raman spectroscopy for the evaluation of organic contents, and ICP-AES/MS for the measurement of elemental composition and concentration. Spectrofluorometry was also utilized to establish if the content of optical brightener was homogenous in all paper types. The spectroscopic techniques didn’t require any sample preparation except for cutting the papers in pieces, according to their “geographical” place in the sheets. The ICP-AES and ICP-MS analyses required sample preparation in form of cutting the pieces and digesting each of them with acid and hydrogen peroxide in digestion bombs. After the digestion the samples were diluted with purified water. The results showed that NIR and spectrofluorometry couldn’t differentiate samples within one sheet of all paper types, although NIR made a distinction between the office paper samples. FT-IR on the other hand could distinguish between samples in one group from samples belonging to another group further away within same sheet. The elemental concentrations of sample pieces were also significantly different within same sheet of office paper, paper towel and corrugated paperboard. This elemental distinction could be made in both ICP-AES and ICP-MS. The results from Raman spectroscopy were unusable due to gained broad bands as spectra instead of peaks, the reason for that is high fluorescence. Different laser intensities were used with no change in result.

Abstract [sv]

Syftet med arbetet var att undersöka homogeniteten hos papper med avseende på sammansättningen av grundämnen, organiska komponenter samt optiskt vitmedel. Tre olika sorters papper användes A4 papper, hushållspapper och wellpapp. Tekniker som användes för detta syfte var ICP-AES (inductively coupled plasma-atomic emission spectroscopy) och ICP-MS (inductively coupled plasma-mass spectroscopy) för koncentrationsbestämning av element. NIR (near-infrared spectroscopy) , FT-IR (fourier transform-infrared spectroscopy) och Raman spektroskopi användes för analys av de organiska komponenterna i pappret samt spektrofluorometri för mätning av optiskt vitmedel och andra fluorescerande molekyler i pappret. Provupparbetning krävdes för analys med ICP-AES och ICP-MS. De olika papperstyperna upplöstes med olika sammansättning av syra och väteperoxid i Uhrbergsbomber, efter upphettning kyldes proverna till rumstemperatur och späddes med milli-Q vatten. Samma prover som användes för ICP-AES analyserna späddes med thallium internstandard innan analys med ICP-MS. De andra spektroskopiska teknikerna krävde ingen provupparbetning, annat än urklippning av pappersbitar som skulle passa provbehållaren. Resultaten visade att ICP-AES/MS kunde diskriminera olika element i olika koncentrationer genom ett helt ark. Detta gällde för alla papperstyper. FT-IR var också diskriminernande för vissa prover inom alla papperssorter, medan resultaten från NIR och spektrofluorometri analyserna inte kunde urskilja olika prover inom ett och samma ark. Detta tyder på att dessa instrument inte kan uppvisa någon inhomogenitet hos pappret med avseende på organisk sammansättning respektive innehållet av optiskt vitmedel.

Place, publisher, year, edition, pages
2012. , 66 p.
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-177271OAI: diva2:539886
Physics, Chemistry, Mathematics
Available from: 2012-07-09 Created: 2012-07-05 Last updated: 2012-07-09Bibliographically approved

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