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978-3-8439-0275-5, Reihe Lebensmittelchemie

Roland von der Recke
Structures of anaerobic and photolytic transformation products of selected polybrominated flame retardants and their presence in environmental samples

161 Seiten, Dissertation Universität Hohenheim Stuttgart-Hohenheim (2011), Softcover, A5

Zusammenfassung / Abstract

Many polybrominated substances are used as flame retardants in plastics, textiles and electronics. However, these brominated flame retardants can end up in the environment and enrich in the environment. Two classes were investigated in this doctoral thesis: Polybrominated biphenyls (PBBs) and 2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE).

PBBs were the first commercially produced and used BFRs in the United States of America. Their usage was reduced abruptly in the mid-1970s as a result of an environmental contamination incident in Michigan. However, PBB residue patterns often differed from technical PBB mixtures and contained several unknown PBB congeners, which are supposed to be metabolites, which were formed from higher brominated PBBs by reductive debromination. Therefore, anaerobic and photolytic transformation studies were performed using the technical mixtures and synthesized decabromobiphenyl (PBB 209).

The obtained transformation products were purified and subjected to radiation experiments and their secondary products examined. By the end, the structures of 24 hitherto unknown PBBs could be identified, including all unknown key congeners in the environmental samples.

An hitherto organobromine contaminant originally detected in the blubber extract of a hooded seal (Cystophora cristata) from the Barents Sea was identified as DPTE. DPTE is the main component of the BFR Bromkal 73-5, which was produced by Chemische Fabrik Kalk (Cologne) from the mid-1970s. No production volumes or other manufacturers were mentioned in the literature, so that no reference was commercially available. Therefore, DPTE was synthesized by electrophilic bromination of allyl-2,4,6-tribromophenyl ether (ATE).

Besides DPTE in seal blubber, its starting material ATE and the likewise synthesized 2-bromoallyl-2,4,6-tribromophenyl ether (BATE) were also detected. The parallel study of brain samples of the same animals showed that ATE, BATE and DPTE were 30 times enriched in brain relative to polychlorinated biphenyls (PCBs) and PBDEs. This indicated that these three compounds could overcome the blood–brain barrier more than other halogenated pollutants.

To reconstruct the transformation pathway of DPTE in the environment, DPTE was used as substrate for anaerobic transformation studies. Besides the main product ATE and the by-product 2,4,6-tribromophenol two beyond unknown compounds were formed.