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Zürich, Switzerland

Gabriel S.J.,BAM Federal Institute of Materials Research and Testing | Steinhoff R.F.,Vladimir Prelog Weg | Pabst M.,Vladimir Prelog Weg | Schwarzinger C.,Johannes Kepler University | And 4 more authors.
Rapid Communications in Mass Spectrometry | Year: 2015

Rationale The ionization of polystyrenes in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is typically achieved by the use of silver salts. Since silver salts can cause severe problems, such as cluster formation, fragmentation of polymer chains and end group cleavage, their substitution by alkali salts is highly desirable. Methods The influence of various cations (Ag+, Cs+ and Rb+) on the MALDI process of polystyrene (PS) mixtures and high mass polystyrenes was examined. The sample preparation was kept as straightforward as possible. Consequently, no recrystallization or other cleaning procedures were applied. Results The investigation of a polystyrene mixture showed that higher molecular polystyrenes could be more easily ionized using caesium, rather than rubidium or silver salts. In combination with the use of DCTB as matrix a high-mass polymer analysis could be achieved, which was demonstrated by the detection of a 1.1 MDa PS. Conclusions A fast, simple and robust MALDI sample preparation method for the analysis of ultra-high molecular weight polystyrenes based on the use of DCTB and caesium salts has been presented. The suitability of the presented method has been validated by using different mass spectrometers and detectors. Copyright © 2015 John Wiley & Sons, Ltd. Source


Valla M.,Vladimir Prelog Weg | Stadler D.,Vladimir Prelog Weg | Mougel V.,Vladimir Prelog Weg | Coperet C.,Vladimir Prelog Weg
Angewandte Chemie - International Edition | Year: 2016

Re oxo alkylidene surface species are putative active sites in classical heterogeneous Re-based alkene-metathesis catalysts. However, the lack of evidence for such species questions their existence and/or relevance as reaction intermediates. Using Re(O)(=CH-CH=CPh2)(OtBuF6)3(THF), the corresponding well-defined Re oxo alkylidene surface species can be generated on both silica and silica-alumina supports. While inactive on the silica support, it displays very good activity, even for functionalized olefins, on the silica-alumina support. Al-ctivation: Supporting a well-defined Re oxo alkylidene on a silica-alumina support gives a highly active metathesis catalyst, while the corresponding species on silica is inactive. This work shows the importance of Lewis acid sites in activating these catalysts. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Borovinskaya O.,Vladimir Prelog Weg | Burger M.,Vladimir Prelog Weg | Flamigni L.,Vladimir Prelog Weg | Gschwind S.,Vladimir Prelog Weg | And 5 more authors.
Chimia | Year: 2014

Inductively coupled plasma mass spectrometry is increasingly used for non-traditional applications such as the analysis of solids at high spatial resolution when combined with laser ablation or the analysis of engineered nanoparticles. This report highlights recent projects and discusses the potentials and limitations these techniques offer. High-resolution laser ablation instrumentation allows element imaging at the μm-scale and can, therefore, be applied to, e.g., the mapping of metal isotope-labeled antibodies in biological tissues. Despite these advancements, the quantitative analysis of laser-produced aerosols is still a major concern. Here, the accuracy of analysis was found to strongly depend on particle size distribution but also on the morphology and composition of particles. In order to achieve a controlled supply of nanoparticles for analysis by inductively coupled plasma mass spectrometry, a dedicated microdroplet injection system was developed and characterized. This system allows a reproducible injection of single nanoparticles together with internal standards to determine their mass and composition. © Schweizerische Chemische Gesellschaft. Source

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