Listen
4 Ergebnisse
Filter
Einstellungen
Suchergebnisse
Veröffentlichung Hygienische Beurteilung von Stoffen zur Herstellung von Elastomeren im Kontakt mit Trinkwasser(2014)Werkstoffe, die bestimmungsgemäß in Kontakt mit Trinkwasser kommen, haben zum Schutz der menschlichen Gesundheit besondere Anforderungen zu erfüllen. Solche Anforderungen sind gesetzlich verbindlich in der Trinkwasserverordnung festgelegt. Soweit die hygienische Beurteilung von Elastomerprodukten betroffen ist, kann ersatzweise die Elastomerleitlinie des Umweltbundesamts (UBA) herangezogen werden, die sich hauptsächlich mit der Bewertung der Ausgangsstoffe und ihrer Migration befasst. Der vorliegende Aufsatz diskutiert die spezifischen Forderungen und die Prinzipien des Verfahrens.
© www.gupta-verlag.comVeröffentlichung Modelling migration of substances from polymers into drinking water(2017) Mercea, P.V.; Kalisch, A.; Ulrich, M.; Schuster, RamonaIn a first part of this work the permeation through and diffusion/migration from high density polyethylene,polybutylene, polypropylene and cross linked polyethylene films was investigated experimentally with three different methods to determine diffusion coefficients in these polyolefins for a series of additives, their degradation products and other organic substances in the 20-60 ˚C temperature range. The experimental methods used were dynamic permeation through additive free the polymer films, kinetic desorption from additivated films into water and kinetic migration from additivated into additive free polymer films. It was found that in general the temperature dependence of the obtained diffusion coefficients was well represented by the Arrhenius law. Some of these results also suggested that the contact of the polyolefins with water had an influence on the magnitude of the diffusion coefficients and on their apparent activation energy of diffusion.In the second part of this work the obtained pools of diffusion coefficients for each of the investigated polymers were used to develop an approach to estimate theoretically and without any further experimentation "conservative" diffusion coefficients for any organic substance, with molecular mass ranging from 50 to 1250 g/mol, diffusing in these polymers at temperatures between 15 and 85 ˚C. The possibility to estimate such conservative diffusion coefficients is very important when it comes to use efficiently migration modelling as an alternative method to test the compliance of polymeric articles with the existing national and/or European standards for drinking water. The use of polymer specific diffusion coefficients in migration modelling is required in the framework of the "Migration modelling guideline" recommendation of the German Environment Agency. Quelle: https://www.sciencedirect.com/Veröffentlichung Contaminants migrating from crossed-linked polyethylene pipes and their effect on drinking water odour(2019) Kalweit, Cynthia; Stottmeister, Ernst; Rapp, ThomasThe formation potential of contaminants diffusing from cross-linked polyethylene (PE-X) pipes and their impact on the odour of drinking water was determined. Three types of PE-X material, Pe-Xa, PE-Xb and PE-Xc, were extensively assessed by performing migration tests following EN 1420 and EN 12873-1. Migration waters were analysed for their threshold odour number (TON). The same samples were investigated by two gas chromatography-mass spectrometry methods: screening and olfactometry. Most of the PE-X materials failed the German regulation of TON <2 for cold water and TON <4 for warm water. PE-Xb material caused the strongest odour and also released the highest amount of contaminants. Metilox, 7,9-di-tert-butyl-1-oxaspiro(4,5)deca-6,9-diene-2,8-dione, 3,5-di-tert-butyl-4-hydroxybenzaldehyde and 2,6-di-tert-butyl-p-benzoquinone (2,6-DtBQ) were the most often detected substances leaching from the tested plastic materials. However, no odour was perceived for most of these substances. Methyl tert-butyl ether (MtBE) and 2-tert-butylphenol are believed to contribute to the sensory problem in the migration water among other substances such as tert-amyl methyl ether, 2,2,2,5-tetramethyltetrahydrofuran, toluene or xylene. In total ten specific descriptions characterized the odour of the individual contaminants: ethereal, fresh, solvent, sweet, fruity, floral, unsavoury, pungent, aromatic and chemical. Quelle: https://www.sciencedirect.comVeröffentlichung Quantification and stability assessment of 7,9-di.tert-butyl-1-oxaspiro(4,5)deca-6,9-diene-2,8-dione leaching from cross-linked polyethylene pipes using gas and liquid chromatography(2023) Berger, Sabrina; Kalweit, Cynthia; Kämpfe, Alexander David; Rapp, ThomasThis study assesses the formation and stability of the water contaminant 7,9-di-tert-butyl-1-oxaspiro(4,5)deca-6,9-diene-2,8-dione ([1]) which repeatedly occurs in the migration waters of cross-linked polyethylene (PE-X) pipes. In aqueous solution [1] is partially transformed to 3-(3,5-di-tert-butyl-1-hydroxy-4-oxo-2,5-cyclohexadien-1-yl)propionic acid ([2]). For a better understanding of the formation of [1] and its transformation into [2] an analytical method was established to allow the analysis of both species separately. Because of thermal instability [2] cannot be detected with GC-MS. Therefore, two methods were validated for a reliable and reproducible quantification: GC-MS for [1] and HPLC-MS/MS for both [1] and [2]. Comparative measurements of migration waters from PE-X pipes using GC-MS and HPLC-MS/MS methods showed that the concentrations of [1] detected with GC-MS corresponds to the sum of [1] and [2] measured with HPLC-MS/MS. In the migration waters [1] was detected in higher concentrations than [2]. The highest concentrations of [1], detected with GC-MS, were > 300 (micro)g/L. The longer the materials are stored without contact with water, the more [1] is measured in the migration waters. Most of the previous values reported in the literature for [1] were based on semi-quantification. Hence, we compared results of the semi-quantitative determination according to EN 15768 with those of a quantitative method with a standard. The results gained with the semi-quantitative method represent less than 50% of the quantified values for the amount leaching from the pipes, which means that the semi-quantification method according to EN 15768 leads to a significant underestimation of [1]. Finally, stability assessment showed that [1] developed an equilibrium with [2] under acidic conditions, whereas it will completely be transferred to [2] at pH 10. At pH 7, it takes more than 50 days for [1] to reach an equilibrium with [2]. However, at increasing the temperature to 60 ËÌC, [1] will be rapidly transformed into [2]. Besides [1] and [2], other currently unknown degradation products are formed. As there is no comprehensive toxicological assessment for both substances available today, our findings underline the need for regulatory consequences. © 2023 Elsevier Ltd. All rights reserved.