Anal. Chem. 2001, 73, 4951-4957
A GC/ECNI-MS Method for the Identification of Lipophilic Anthropogenic and Natural Brominated Compounds in Marine Samples Walter Vetter*
Friedrich Schiller University Jena, Department of Food Chemistry, Dornburger Strasse 25, D-07743 Jena, Germany
GC/ECNI-MS in both the full scan and selected ion monitoring modes was applied to study the patterns of brominated compounds in the blubber of marine mammals from a variety of locations. The adipose tissue of one polar bear was also studied. Occurrence of three major residues originating from the use of brominated flameretardants (PBDE 47, 99, and 100) and several potential naturally occurring brominated compounds was studied in the samples. A series of three major natural brominated compounds (BC-1, BC-2, BC-3) recently identified in dolphins from Australia was included in this study. Two further brominated compounds, BC-10 and BC-11, were studied for the first time. ECNI-MS full scan spectra were obtained for BC-3 and BC-10. A natural mixed halogenated compound (MHC-1) and an unknown brominated compound (UBC-1) were investigated as well. Evidence for the natural production of these secondary metabolites and their bioaccumulation in higher organisms as well as analytical protocols for their detection in the environment are presented. Some of these naturally occurring compounds may be misinterpreted as anthropogenic brominated compounds. In ECNI-MS, brominated compounds are usually identified by the detection of the fragment ions m/z 79 ([79Br]-) and m/z 81 ([81Br]-). In this work, it is shown that monitoring of additional ion traces corresponding to [Br2]- (160 type), [HBr2]- (161 type), [BrCl]- (116 type), and [HBrCl]- (117 type) fragment ions allows distinguishing between different classes of brominated compounds. This technique was used to demonstrate that UBC-1 is neither a PBDE nor a PBB congener, whereas a second mixed halogenated compound (MHC-2) was identified as a result of the ECNIMS response at m/z 114/116. Studies on blubber extracts of marine mammals from four continents resulted in the detection of significant differences in the global distribution of brominated compounds. Our results suggest that naturally occurring organobromines are more abundant than anthropogenic brominated compounds in several regions of the world. Detection of brominated compounds has attracted an increasing interest in environmental science. Gas chromatographic * Phone: 0049 3641 949 657. Fax: 0049 3641 949 652. E-mail:
[email protected]. 10.1021/ac015506u CCC: $20.00 Published on Web 09/12/2001
© 2001 American Chemical Society
Figure 1. Structure of single components in formulations of brominated flame-retardants. From top left to bottom right: 2,2’,4,4’tetrabromodiphenyl ether (PBDE 47), 2,2’,4,4’,5-pentabromodiphenyl ether (PBDE 99), 2,2’,4,4’,6-pentabromodiphenyl ether (PBDE 100), and 2,2’,5,5’-tetrabromobiphenyl (PBB 52).
separation followed by ECNI-MS detection in the SIM mode using m/z 79 and m/z 81 is a highly sensitive and selective method for the determination of brominated compounds in environmental samples.1 These studies identified brominated flame-retardants (BFRs) in several environmental compartments with a tendency toward increasing global concentrations.2 These studies have further suggested that the brominated trace chemicals observed in the tissues of higher organisms originate from the use of BFRs. Major BFR pollutants are polybrominated diphenyl ethers (PBDEs), which have been detected in numerous environmental samples.1 Relevant PBDE congeners occurring in a variety of samples include PBDE 47 and, to a lesser extent, PBDE 99 and 100 (Figure 1).1,3,4 PBDE 47 and 99 are found in the technical formulation pentabromodiphenyl ether (Bromkal 70-5 DE) at ∼40%.1,5 Lower quantities are also found for PBDE 100.6 Another class of nonpolar BFRs is polybrominated biphenyls (PBBs; for an example, see Figure 1), but PBB concentrations in environmental samples were generally lower than those of the PBDEs.1 In a recent study of marine mammals from Australia, several other previously unknown brominated compounds were detected (1) de Boer, J.; de Boer, K.; Boon, J. P. In The Handbook of Environmental Chemistry; Paasivirta, J., Ed.; Springer-Verlag: Berlin, Heidelberg, 2000, Vol. 3, Part K, pp 61-95. (2) Nore´n, K.; Meironyte´, D. Organohalogen Compd. 1998, 38, 1-4. (3) van Bavel, B.; Sundelin, E.; Lillba¨ck, J.; Lindstro ¨m, G. Organohalogen Compd. 1999, 40, 359-362. (4) Ikonomou, M. G.; Fischer, M.; He, T.; Addison, R. F.; Smith, T. Organohalogen Compd. 2000, 47, 77-80. (5) Sellstro ¨m, U. Doctoral Thesis, 1999, University of Stockholm. ISBN 91-7265023-0. (6) Strandberg, B.; Dodder, N. G.; Basu, I.; Hites R. A. Environ. Sci. Technol. 2001, 35, 1078-1083.
Analytical Chemistry, Vol. 73, No. 20, October 15, 2001 4951
and identified as naturally occurring brominated compounds.7 This study also suggested that there are regional differences in the Br-selective residue pattern. The goal of the present study is to provide data that confirms this hypothesis. In addition, protocols enabling one to distinguish between different classes of brominated compounds were developed. MATERIALS AND METHODS Sample Origin of Blubber Samples. Blubber samples were available from two harp seals (Phoca groenlandica) and two hooded seals (Cystophory cristata) from Jan Mayen (Northern Sea/ Europe). Additionally, samples of three harp seals from Svalbard were analyzed. A pooled sample of eight gray seals (Halichoerus grypus) from western Iceland was investigated, as well. Adipose tissue of a polar bear (Ursus maritimus) from an animal collected 118.5 km north of Horn, Northwest Iceland, and two blubber samples of gray seals from the Baltic Sea, one collected at Stralsund, the other at another, unknown place along the German Baltic coast, were also part of this study. Samples of three harbor porpoises (Phocoena phocoena) and two samples of harbor seals (Phoca vitulina) from the German coast of Lower Saxony (North Sea) were available. Two of 14 samples of monk seals (Monachus monachus) from Mauretania (West-Sahara, Africa) and two Weddell seals (Leptonychotes Weddelli) from Antarctica (72° 52′ S, 19° 25′ W) were analyzed, as well. Two samples of pygmy sperm whales (Kogia breviceps) and one melon-headed whale (Peponocelphala electra) from Queensland represented samples from Australia. Sample Cleanup Methods. Samples were extracted using the microwave-assisted extraction technique (performed in either closed or open vessels) and cleaned up using gel permeation chromatography for lipid removal. Silica gel adsorption chromatography was used for the separation of PCBs and similar compounds from the more polar aliphatic/alicyclic chloropesticides and brominated compounds.8,9 Additional extracts were available from samples previously screened for other substances. These samples (hooded seals, harp seals, gray seals, polar bear, Weddell seals, harbor seals, and porpoises) were cleaned up by acid digestion followed by repeated H2SO4 treatment and liquid/ liquid partitioning into n-hexane. The remaining fat matrixes (
