title: Polyhalogenated carbazoles in sediments of Lake Michigan: a new discovery.
abstract: Previously unknown halogenated compounds were detected during the analysis of halogenated flame retardants in two sediment cores collected from Lake Michigan. Gas chromatography coupled with high- or low-resolution mass spectrometry (MS) was used to determine the chemical structures for a total of 15 novel polyhalogenated carbazoles (PHCs) with the general molecular formula C12H9-x-y-zNClxBryIz. On the basis of the mass spectra generated by electron impact (EI) and electron capture negative ionization (ECNI) MS, eight PHCs were tentatively identified as polybrominated carbazoles, while the others were mixed halogenated carbazoles containing, in addition to bromine, either chlorine or iodine or both. Patterns of halogen substitution of PHCs included Br2 to Br5, ClBr2, ClBr3, ClBr4, ClBr3I, Br4I, and Br3I2. 3,6-Dibromocarbazole and 1,3,6,8-tetrabromocarbazole were also found among the PHCs. Profiles of the concentration versus depth of sediment at the two sites showed various patterns among polybrominated carbazoles. The abundance of mixed halogenated carbazoles peaked at depths of 12-16 cm, remained at relatively constant levels in deeper sediment, but declined markedly in more recently deposited sediments. This is the first study discovering the seven mixed halogenated carbazoles in the environment. Detailed methods for their detection and identification are provided.
authors.affiliation: School of Public Health, University of Illinois at Chicago , Chicago, Illinois 60612, United States.
authors.forename: Jiehong
authors.initials: J
authors.lastname: Guo
authors.forename: Da
authors.initials: D
authors.lastname: Chen
authors.forename: Dave
authors.initials: D
authors.lastname: Potter
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Rockne
authors.forename: Neil C
authors.initials: NC
authors.lastname: Sturchio
authors.forename: John P
authors.initials: JP
authors.lastname: Giesy
authors.forename: An
authors.initials: A
authors.lastname: Li
mesh_terms: D002227:Carbazoles / Q000032:analysis*; D002849:Chromatography, Gas; D004583:Electrons; D005411:Flame Retardants / Q000032:analysis; D019015:Geologic Sediments / Q000737:chemistry*; D054879:Halogenation; D060106:Lakes / Q000737:chemistry*; D013058:Mass Spectrometry; D008824:Michigan
chemical_list: D002227:Carbazoles; D005411:Flame Retardants