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Eingeladener Vortrag
- nein (5)
In this work, a study of electrochemical conversion was performed to elucidate different degradation pathways of the heterocyclic brominated flame retardants 1,3,5-Tris-(2,3-dibromopropyl)-1,3,5-triazine-2,4,6-trione (TDBP-TAZTO) and 2,4,6-Tris-(2,4,6-tribromo-phenoxy)-1,3,5-triazine (TTBP-TAZ). EC/MS was used to simulate the (bio)-transformation processes and to identify possible transformation products (TPs) which have never been reported before. For TDBP-TAZTO, six new TPs were observed after the electrochemical oxidation (applied potential of 0 to 1,800 mV vs. Pd/H2). In case of TTBP-TAZ, seven debromination products were generated with an applied potential of 0 to 2,200 mV vs. Pd/H2. The main degradation pathways confirmed by high resolution mass spectrometry for both compounds were hydroxylation, debromination as well as dehydrobromination.
1,3,5-Tris-(2,3-dibromopropyl)-1,3,5-triazine-2,4,6-trione (TDBP-TAZTO) is an emerging brominated flame retardant which is widely used in several plastic materials (electric and electronic equipment, musical instruments, automotive components).
However, until today, no photochemical studies as well as the identification of possible phototransformation products (PTPs) were described in literature. Therefore, in this study, UV-(C) and simulated sunlight irradiation experiments were performed to investigate the photolytic degradation of TDBP-TAZTO and to identify relevant PTPs for the first time. The UV-(C) Irradiation experiments show that the photolysis reaction follows a first-order kinetic model. Based on this, the photolysis rate constant k as well as the half-life time t1/2 were calculated to be k = (41 ± 5 ×10−3) min−1 and t1/2=(17±2) min. In comparison, a minor degradation of TDBP-TAZTO and no formed phototransformation products were obtained under simulated sunlight. In order to clarify the photochemical behavior, different chemicals were added to investigate the influence on indirect photolysis: (i) H2O2 for generation of hydroxyl radicals and (ii) two quenchers (2-propanol, sodium azide) for scavenging oxygen species which were formed during the irradiation experiments. Herein, nine previously unknown PTPs of TDBP-TAZTO were detected under UV-(C) irradiation and identified by HPLC-(HR)MS. As a result, debromination, hydroxylation, and dehydrobromination reactions could be presumed as the main degradation pathways by high-resolution mass spectrometry. The direct as well as the OH radical-induced indirect photolysis were observed.
High-performance liquid chromatography tandem mass spectrometry (HPLC–MS/MS) was applied to sterospecifically quantify the content of α-, β-, and γ-hexabromocyclododecane (HBCD) in six fish species from the Norwegian Etnefjorden. A combination of a β-PM cyclodextrin and an achiral column enabled the paired chromatographic separation of the stereoisomers in the order (-)-α-, (+)-α-, (-)-β-, (+)-β-, (+)-γ- and, (-)-γ-HBCD. The limits of detection were in the range of 6–21 pg g-1 depending on the stereoisomer and the concentrations of α-, β-, and γ-HBCD in fillets ranged from <5.4 ng g-1 to 11.1 µg g-1 lipid weight. α-HBCD enantiomers were throughout dominating, and in most cases the accumulation of the respective first eluted enantiomers ((-)-α-, (-)-β- and (+)-γ-HBCD) was observed. Deviations from the racemic EF-value were considered to be significant if it was outside of the expanded uncertainty range for each of the racemic HBCD-ratios. The composition of HBCD isomers varied between the investigated fish species and the relative high values for the γ-HBCD concentrations for the bottom-dwellers flounder and thorny skate seems to echo the HBCD pattern of ocean sediments.
Enantiomerenspezifischer Vergleich von HBCD-Gehalten maritimer Lebewesen zweier norwegischer Fjorde
(2010)
The interconversion of the stereoisomers contained in technical 1,2,5,6,9,10-hexabromocyclododecane, a major brominated flame retardant increasingly found in the environment and in biota, was investigated at elevated temperatures. The application of pure enantiomers of the three constituents α-, β-, and γ-HBCD enabled the unambiguous elucidation of the individual isomerisation reactions as well as the quantification of all respective rate constants. At 160 °C the rate constants range over two orders of magnitude from 1.50 × 10-3 to 1.88 × 10-5 mol(%) s-1. A preliminary mechanistic explanation for the differences of the rate constants which govern the composition of HBCD diastereomers at equilibrium is given.