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Monohydroxylated Polybrominated Diphenyl Ethers (OH-PBDEs) and Dihydroxylated Polybrominated Biphenyls (Di-OH-PBBs): Novel Photoproducts of 2,6-Dibromophenol
journal contribution
posted on 2015-12-15, 00:00 authored by Hongxia Zhao, Jingqiu Jiang, Yanli Wang, Hans-Joachim Lehmler, Garry
R. Buettner, Xie Quan, Jingwen ChenHydroxylated polybromodiphenyl ethers
(OH-PBDEs) are emerging aquatic
pollutants, but their origins in the environment are not fully understood.
There is evidence that OH-PBDEs are formed from bromophenols, but
the underlying transformation processes remain unknown. Here, we investigate
if the photoformation of OH-PBDEs from 2,6-dibromophenol in aqueous
solution involves 2,6-bromophenoxyl radicals. After the UV irradiation
of an aqueous 2,6-dibromophenol solution, HPLC–LTQ-Orbitrap
MS and GC–MS analysis revealed the formation of a OH-PBDE and
a dihydroxylated polybrominated biphenyl (di-OH-PBB). Both dimeric
photoproducts were tentatively identified as 4′-OH-BDE73 and
4,4′-di-OH-PBB80. In addition, three debromination products
(4-OH-BDE34, 4′-OH-BDE27, and 4,4′-di-OH-PBBs) were
observed. Electron paramagnetic resonance spectroscopy revealed the
presence of a 2,6-dibromophenoxyl radical with a six-line spectrum
(aH (2 meta) = 3.45 G, aH (1 para) = 1.04 G, g = 2.0046) during irradiation
of a 2,6-dibromophenol solution in water. The 2,6-dibromophenoxyl
radical had a relatively long half-life (122 ± 5 μs) according
to laser flash photolysis experiments. The para–para C–C and O–para-C couplings of these
2,6-dibromophenoxyl radicals are consistent with the observed formation
of both dimeric OH-PBDE and di-OH-PBB photoproducts. These findings
show that bromophenoxyl radical-mediated phototransformation of bromophenols
is a source of OH-PBDEs and di-OH-PBBs in aqueous environments that
requires further attention.
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HPLCMonohydroxylated Polybrominated Diphenyl EthersGCsolutiondimeric photoproductsdihydroxylated polybrominated biphenylUV irradiationtransformation processes1.04 GMSradical3.45 Gresonance spectroscopydibromophenollaser flash photolysis experimentsDihydroxylated Polybrominated BiphenylsbromophenolparabromophenoxylaHdibromophenoxylfindings show
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