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Garching bei Munchen, Germany

Huck C.W.,Institute for Radiochemistry
Journal of Pharmaceutical and Biomedical Analysis | Year: 2014

During the last couple of years great advances in vibrational spectroscopy including near-infrared (NIR), mid-infrared (MIR), attenuated total reflection (ATR) and imaging and also mapping techniques could be achieved. On the other hand spectral treatment features have improved dramatically allowing filtering out relevant information from spectral data much more efficiently and providing new insights into the biochemical composition. These advances offer new possible quality control strategies in phytomics and enable to get deeper insights into biochemical background in terms of medicinal relevant questions. It is the aim of the present article pointing out the technical and methodological advancements in the NIR and MIR field and to demonstrate the individual methods efficiency by discussing distinct selected applications. © 2013 Elsevier B.V.

Starting from known structures of the modifications of As2O5 we investigate the results of relaxations in DFT calculations performed at different fixed volumes per formula unit on keeping the axis relations and the symmetry of the original space group. We analyse the correlation between the topology of a structure, i.e. the co-ordination geometry and the distances observed, with the charges of the atoms as derived form a Bader analysis of the electron distribution resulting from a DFT relaxation. A similar study is done on the changes of the structure and the charges as a result of a relaxation without such a symmetry bias giving a new hitherto unknown possible high pressure structure. © 2015 Elsevier Masson SAS. All rights reserved.

Beck H.P.,Institute for Radiochemistry
Zeitschrift fur Kristallographie | Year: 2012

The crystal chemistry of many AB2O6 compounds is summarized in family trees comparing the crystal symmetry of several structures in group-subgroup relations. In this second part of a series the largest family derived from a hexagonally close packed arrangement of anions is described. On reducing the symmetry, different choices of octahedral sites for A and B cations and voids lead to four branches - the Rosiaite-, the ZnTa2O 6-, the columbite- and the rutile-branch. We trace the reasons for the specific distribution patterns of the cations in the individual compounds by comparing long range contributions, i.e. the Madelung Part of Lattice Energy (MAPLE), and local effects represented by bond valence calculations according to I. D. Brown. Long range effects largely determine the choice of sites in the respective space groups, however, small local adjustments play a decisive role for the stability of a specific structural modification. Such mechanismsultimately impose how the structure of an individual compound deviates from an ideally packed arrangement. We discuss the difference between the ideal structures and the real examples given in the family tree by defining a sort of deformation tensor and a measure of similarity, and we describe and depict the anisotropic deformation by a strain tensor. © by Oldenbourg Wissenschaftsverlag, Müchen.

Vukics V.,University of Innsbruck | Guttman A.,University of Innsbruck | Guttman A.,Institute for Radiochemistry
Mass Spectrometry Reviews | Year: 2010

Flavonoids are secondary plant metabolites of great structural variety and high medicinal significance. The search for new chemical entities and the quality control of flavonoid containing natural products require easy-to-use but reliable and robust analytical methodologies. For structural elucidation of flavonoids and their glycosides, nuclear magnetic resonance (NMR) and mass spectroscopy (MS) are the generally used techniques. In phytochemical analyses, however, high amounts of flavonoids are difficult to isolate for NMR, thus low sample volume requiring MS based methods are emerging. This review summarizes and compares currently available methods for structural elucidation of flavonoids by LC-MS and LC-MSn, and focuses on the identification options of unknown flavonoid glycosides in complex samples (e.g., plant extracts) with the emphasis on the differentiation of isomeric compounds. © 2008 Wiley Periodicals, Inc.,.

Kautenburger R.,Institute for Radiochemistry
Journal of Analytical Atomic Spectrometry | Year: 2011

Geological clay formations are often considered as a host rock for a future waste repository. Many studies concerning sorption or desorption experiments of radionuclides or other toxic metals onto/from geological samples like clay are performed with batch techniques where only small amounts of the homogenised clay samples are in contact with the appropriate metals diluted in high volumes of aqueous solutions. This can lead to a high leaching of metal ions originating from the clay. The leached elements can considerably increase the background concentration of many isotopes, and they may also influence the results of the sorption/desorption experiments due to their competition with the used metal ions. This study focuses on this problem by analysing element leaching of clay during the batch procedure. After characterisation of the used Opalinus clay (OPA), element leaching was performed by extraction of homogenised clay samples from a bore hole with two different leaching solutions, Milli-Q water and, in contrast, synthetic porewater (PW) with a high ionic strength. After centrifugation, the leached elements in the supernatant were analysed by inductively coupled plasma-mass spectrometry (ICP-MS). Depending on the used extraction solution different elemental compositions in the leachate can be determined. The leaching of OPA with Milli-Q water leads to a dissolution of mainly anionic element species, whereas the use of PW leads to a release of mainly cationic metal ions. In particular, metals like Al, Fe, V, Cr, Co, Ni, Sr, Ba and U (beside the present PW ions) can be found in the leachates. © 2011 The Royal Society of Chemistry.

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