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Veröffentlichung Analysis of polyethylene microplastics in environmental samples, using a thermal decomposition method(2015) Dümichen, Erik; Bannick, Claus Gerhard; Barthel, Anne-Kathrin; Braun, Ulrike; Brand, Kathrin; Jekel, Martin; Senz, RainerSmall polymer particles with a diameter of less than 5 mm called microplastics find their way into the environment from polymer debris and industrial production. Therefore a method is needed to identify and quantify microplastics in various environmental samples to generate reliable concentration values. Such concentration values, i.e. quantitative results, are necessary for an assessment of microplastic in environmental media. This was achieved by thermal extraction in thermogravimetric analysis (TGA), connected to a solid-phase adsorber. These adsorbers were subsequently analysed by thermal desorption gas chromatography mass spectrometry (TDS-GC-MS). In comparison to other chromatographic methods, like pyrolyse gas chromatography mass spectrometry (Py-GC-MS), the relatively high sample masses in TGA (about 200 times higher than used in Py-GC-MS) analysed here enable the measurement of complex matrices that are not homogenous on a small scale. Through the characteristic decomposition products known for every kind of polymer it is possible to identify and even to quantify polymer particles in various matrices. Polyethylene (PE), one of the most important representatives for microplastics, was chosen as an example for identification and quantification.Quelle: http://www.sciencedirect.comVeröffentlichung Quantification and characterisation of activated carbon in activated sludge by thermogravimetric and evolved gas analyses(2018) Braun, Ulrike; Dittmann, Daniel; Jekel, Martin; Ruhl, Aki SebastianAdvanced wastewater treatment with powdered activated carbon (PAC) leads to a spread of PAC into different purification stages of wastewater treatment plants (WWTP) due to recirculation and filter back-wash. Currently, no methods for quantification of PAC in activated sludge are available. In this study, PAC containing activated sludge from four WWTP were examined by two-step thermogravimetric analysis (TGA) with heating up to 600˚C in N2 and subsequently in synthetic air. Direct quantification of PAC according to temperature specific weight losses was possible for one WWTP. Quantification by combining specific mass losses was found to be an alternative direct method, with a detection limit of 1.2% PAC in dry sample mass. Additionally, evolved gas analysis (EGA) by infrared-spectroscopy (FTIR) during TGA revealed interaction mechanisms between PAC and activated sludge. Aliphatic compounds from activated sludge were identified as major substances influenced by PAC. In derivative thermogravimetry (DTG), a typical double peak at approximately 300˚C was found to be related to carbonylic species with increased evolution of acetic acid in aged activated sludge. TGA and EGA are promising tools to understand, control and optimise the application of PAC in advanced wastewater treatment. © 2018 Elsevier Ltd. All rights reserved.Veröffentlichung The challenge in preparing particle suspensions for aquatic microplastic research(2019) Eitzen, Lars; Paul, Sophia; Braun, Ulrike; Ruhl, Aki SebastianThe occurrence of small particles consisting of organic polymers, so-called microplastic (MP), in aquatic environments attracts increasing interest in both public and science. Recent sampling campaigns in surface waters revealed substantial numbers of particles in the size range from a few micrometers to a few millimeters. In order to validate sample preparation, identification and quantification and to investigate the behavior of MP particles and potential toxic effects on organisms, defined MP model particles are needed. Many studies use spherical compounds that probably behave differently compared to irregularly shaped MP found in environmental samples. However, preparation and handling of MP particles are challenging tasks and have been systematically investigated in the present study. Polystyrene (PS) as a commonly found polymer with a density slightly above that of water was selected as polymer type for milling and fractionation studies. A cryogenic ball mill proved to be practical and effective to produce particles in the size range from 1 to 200 Ìm. The yield of small particles increased with increasing pre-cooling and milling durations. Depending on the concentration and the size, PS particles do not completely disperse in water and particles partly creep vertically up along glass walls. Stabilized MP suspensions without use of surfactants that might harm organisms are needed for toxicological studies. The stabilization of PS particle suspensions with ozone treatment reduced the wall effect and increased the number of dispersed PS particles but increased the dissolved organic carbon concentration and changed the size distribution of the particles. © 2018 Elsevier Inc. All rights reserved.Veröffentlichung Kunststoffe und Mikrokunststoffe in der Umwelt(2019) Bannick, Claus Gerhard; Braun, UlrikeVeröffentlichung Harmonisierung von Untersuchungsverfahren für (Mikro-)Plastik in der Umwelt(2019) Braun, Ulrike; Bannick, Claus GerhardVeröffentlichung Determination of microplastic mass content by thermal extraction desorption gas chromatography-mass spectrometry(2021) Wiesner, Yosri; Altmann, Korinna; Braun, UlrikeThe scientific and practical challenge of detecting microplastics (MPs) in the environment in a targeted and rapid manner is solved by innovative coupling of thermogravimetric analysis with mass spectrometric methods. Fast identification and quantitative determination of most thermoplastic polymers and elastomers is possible by using thermal extraction desorption gas chromatography-mass spectrometry (TED-GC-MS). © AuthorsVeröffentlichung Untersuchungsverfahren von Mikroplastikgehalten im Wasser für Praxis und Wissenschaft(2021) Altmann, Korinna; Braun, Ulrike; Heller, ClaudiaZielsetzung des vom Bundesministerium für Bildung und Forschung geförderten Projektes RUSEKU (Repräsentative Untersuchungsstrategien für ein integratives Systemverständnis von spezifischen Einträgen von Kunststoffen in die Umwelt) war es, repräsentative Untersuchungsstrategien für die Detektion von Mikroplastik mittels TED GC/MS in wässerigen Medien zu ermitteln. Dabei wurden verschiedene Probenahmekonzepte und -verfahren für unterschiedliche Fallgestaltungen und Fragestellungen untersucht, sowie neue Filtersysteme entwickelt. Bei der Detektion der Partikel lag der Fokus auf der Anwendung und Weiterentwicklung der ThermoExtraktion/Desorption-Gaschromatographie-Massenspektrometrie (TED-GC/MS) zur Bestimmung von Mikroplastikgehalten. Anwendung fanden die Methoden bei der Beprobung von Flaschenwasser, Waschmaschinenabläufen, dem urbanen Abwassersystem der Stadt Kaiserslautern, sowie in Oberflächengewässern. © AuthorsVeröffentlichung The impact of water released from boehmite nanoparticles during curing in epoxy-based nanocomposites(2021) Waniek, Tassilo; Braun, Ulrike; Sielbernagl, DorotheeThe enhancing effect on mechanical properties of boehmite (y-AlOOH)nanoparticles (BNP) in epoxy-based nanocomposites on the macroscopic scaleencouraged recent research to investigate the micro- and nanoscopic proper-ties. Several studies presented different aspects relatable to an alteration of theepoxy polymer network formation by the BNP with need for further experi-ments to identify the mode of action. With FTIR-spectroscopic methods thisstudy identifies interactions of the BNP with the epoxy polymer matrix duringthe curing process as well as in the cured nanocomposite. The data reveals thatnot the BNP themselves, but the water released from them strongly influencesthe curing process by hydrolysis of the anhydride hardener or protonation ofthe amine accelerator. The changes of the curing processes are discussed indetail. The changes of the curing processes enable new explanation for thechanged material properties by BNP discussed in recent research like alowered glass transition temperature region (Tg) and an interphase formation. © AuthorsVeröffentlichung Smart filters for the analysis of microplastic in beverages filled in plastic bottles(2021) Braun, Ulrike; Altmann, Korinna; Herper, DominikThe occurrence of microplastic (MP) in food products, such as beverages in plastic bottles, is of high public concern. Existing analytical methods focus on the determination of particle numbers, requiring elaborate sampling tools, laboratory infrastructure and generally time-consuming imaging detection methods. A comprehensive routine analysis of MP in food products is still not possible. In the present work, we present the development of a smart filter crucible as sampling and detection tool. After filtration and drying of the filtered-off solids, a direct determination of the MP mass content from the crucible sample can be done by thermal extraction desorption gas chromatography mass spectroscopy (TED-GC/MS). The new filter crucible allows a filtration of MP down to particle sizes of 5 (micro)m. We determined MP contents below 0.01 (micro)g/L up to 2 (micro)g/L, depending on beverages bottle type. This may be directly related to the bottle type, especially the quality of the plastic material of the screw cap. Dependent on the plastic material, particle formation increases due to opening and closing operations during the use phase. However, we have also found that some individual determinations of samples were subjected to high errors due to random events. A conclusive quantitative evaluation of the products is therefore not possible at present. © Taylor&Francis OnlineVeröffentlichung Molecular modelling of epoxy resin crosslinking experimentally validated by near-infrared spectroscopy(2019) Unger, Robin; Braun, Ulrike; Fankhänel, JohannesReliable simulation of polymers on an atomistic length scale requires a realistic representation of the cured material. A molecular modeling method for the curing of epoxy systems is presented, which is developed with respect to efficiency while maintaining a well equilibrated system. The main criterion for bond formation is the distance between reactive groups and no specific reaction probability is prescribed. The molecular modeling is studied for three different mixing ratios with respect to the curing evolution of reactive groups and the final curing stage. For the first time, the evolution of reactive groups during the curing process predicted by the molecular modeling is validated with near-infrared spectroscopy data, showing a good agreement between simulation results and experimental measurements. With the proposed method, deeper insights into the curing mechanism of epoxy systems can be gained and it allows us to provide reliable input data for molecular dynamics simulations of material properties. © 2019 Elsevier B.V.
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