Search

Abstract: Pyrolysis experiments were conducted to elucidate the effects of metal chlorides on the thermal degradation of low-density polyethylene on a continuous pyrolysis temperature range of 600°C to 1100°C. The present work focusses on the ratio of aromatics generated on increasing the pyrolysis temperature in the presence of metal salts, iron(II), iron(III) and copper(II) chlorides. It was observed that beside α,ω-dienes, α-olefins and n-alkanes which are usually observed during the thermal decomposition of polyethylene, the level of aromatics noticeably increases with the addition of metal salts. At high temperatures, the formation of these aromatics took place in such a way that they become the major products when polyethylene is pyrolyzed in presence of FeCl3 and CuCl2. Quantification of the effect of metal salts has been tempted comparing the variation of the ratio of aromatics with pyrolysis temperatures. Mechanisms responsible for the formation of these aromatics in presence of metal salts have been tentatively investigated. They are proposed to result from cyclization/dehydrogenation reactions similar to those observed during the thermal decomposition of polyethylene, but with an increased efficiency due to the metal salts. [Copyright &y& Elsevier]

The presence of trace levels of organic contaminants in the environment is currently an environmental concern. When these contaminants are subjected to environmental transformations, environmental transformation products (ETPs) are obtained, whose structures often remain unknown. The absence of information concerning these new compounds makes them unavailable and consequently makes their environmental detection as well as their (eco)toxicological study impossible. This report describes a multidisciplinary approach that seeks to both anticipate the fate and evaluate the impact of organic environmental contaminants. Our approach consists of three steps. First, isolated and fully characterized transformation products (TPs) of the parent molecule are obtained. In the second step, the parent molecule is subjected to environmentally relevant transformations to identify plausible ETPs. The detection of previously characterized TPs allows the concomitant identification of plausible ETPs. The third step is devoted to the toxicological evaluation of the identified plausible ETPs. Such an approach has recently been applied to furosemide and has allowed the identification of its main TPs. This report now seeks to identify and evaluate toxicologically plausible ETPs of this drug, which is also known as an environmental contaminant. [ABSTRACT FROM AUTHOR]

Abstract: The identification of degradation products generated upon photolysis of estrone (E1), a natural estrogenic hormone, under simulated UV irradiation conditions was addressed by the use of LC-Q-TOF mass spectrometry. The structures of the main degradation products were elucidated, demonstrating how the use of model molecules 5,6,7,8-tetrahydro-2-naphtol (THN), 2-methylcyclopentanone (MCP), labeled molecule estrone D4 (E1-D4), the investigation of the fragmentation pathways of the parent E1, the concurrent use of CID and exact mass measurements permit the characterization of structural modifications induced by photodegradation processes. In the present study, we identified nine major by-products of which seven photoproducts correspond to E1H+ modified in positions other than the C-2, C-4 and C-16 of E1. Most of them showed one to three additional hydroxylations preferentially located on the aromatic ring of the parent E1, which confirms that these products may present environmental risk. Applications to real water samples have been conducted to extend the validity of the present study to environmental samples. [Copyright &y& Elsevier]