Chromatographic and Ionization Properties of Polybrominated Diphenyl Ethers Using GC/ High-Resolution MS with Metastable Atom Bombardment and Electron Impact Ionization Michael G. Ikonomou* Contaminants Science Section, Institute of Ocean Sciences, Fisheries and Oceans Canada, 9860 West Saanich Road, Sidney, British Columbia, Canada, V8L 4B2 Sierra Rayne Department of Chemistry, Box 3065, University of Victoria, Victoria, British Columbia, Canada, V8W 3V6 The chromatographic and ionization properties of 35 polybrominated diphenyl ether (PBDE) congeners were investigated using GC/ HRMS with metastable atom bom- bardment (MAB) and electron impact (EI) ionization. A multiple linear regression model based on bromine substitution patterns and MOPAC calculated physical properties was developed to predict relative GC retention times of individual PBDE congeners. Although five dif- ferent sources of metastable rare gas atoms (He, N 2 , Ar, Xe, and Kr) were investigated with MAB ionization, only MAB-N 2 provided adequate ionization efficiency and predictability. Because of reduced background noise to the MS detector, MAB-N 2 had a lower limit of detection for tetra- and penta-BDEs than EI, despite having a lower sensitivity. Using MAB-N 2 , the molecular ion was always the base peak, with little fragmentation taking place. Conversely, using EI ionization, the [M - nBr] + peak (where n ) 1 -4, depending on the number of Br sub- stituents) was the dominant ion for all PBDE congeners. Multiple linear regression models representing the mo- lecular ion response of PBDE congeners analyzed by GC/ HRMS with MAB-N 2 and EI ionization were also devel- oped using the number and type of Br substituents and ionization potentials. A significantly higher level of pre- dictability was obtained for the MAB-N 2 response model than for EI. Polybrominated diphenyl ethers (PBDEs) are substances used as additive flame retardants in polymeric materials. 1 They are produced in large quantities ( ∼70 000 tons/ year in 1999), 2 are lipophilic and bioaccumulate in a variety of matrixes, 1 and are potential endocrine disrupters. 3 These compounds have been detected in all environmental compartments (sediment, air, water, and biota) and in human tissues at the nanograms-per-gram- micrograms-per-gram levels, 1,4-7 and levels are increasing expo- nentially in arctic regions. 4 There are 209 possible PBDE conge- ners and three major technical mixtures: DeBDE (97-98%deca- BDE), OcBDE (43-44% hepta-BDE, 31-35% octa-BDE; e.g., Bromkal 79-8DE), and PeBDE (24-38%tetra-BDE, 50-62%penta- BDE; e.g., Bromkal 70-5DE). However, current analytical methods and a lack of authentic standards allow identification and quan- titation of only a limited number of PBDE congeners. Because of their prevalence and toxicology, there is much interest in develop- ing reliable analytical methods for all 209 congeners. The use of gas chromatography (GC) coupled with electron- impact (EI) and electron-capture (EC) mass spectrometry (MS) for the analysis of PBDEs has been previously reported. 1,8-11 Electron-capture negative ionization (ECNI), although generally more sensitive and less costly than other ionization methods for PBDE analysis, does not provide information on the molecular ion cluster (as required for qualitative identification), is more subject to brominated interferences, and does not allow the use of 13 C-labeled standards for quantitation. 11-14 Conversely, EI * Corresponding author. Phone: ( 250) 363-6804. Fax: ( 250) 363-6807. E-mail: ikonomoum@ pac.dfo-mpo.gc.ca. (1) de Boer, J.; de Boer, K.; Boon, J. P. 1999. In Paasivirta, J., Ed.; The Handbook of Environmental Chemistry: New Types of Persistent Halogenated Compounds . Springer-Verlag: New York, pp 62-95. (2) Arias, P. A. Brominated flame retardants - an overview, Proceedings of The Second International Workshop on Brominated Flame Retardants, Stockholm, Sweden, May 14-16, 2001; pp 3-4. (3) Meerts, I. A. T. M.; van Zanden, J. J.; Luijks, E. A. C.; van Leeuwen-Bol, I.; Marsh, G.; Jakobsson, E.; Bergman, A.; Brouwer, A. Tox. Sci. 2000 , 56, 95-104. (4) Ikonomou, M. G.; Rayne, S.; Addison, R. F. Environ. Sci. Technol. 2002 , 36, 1886-1892. (5) Ikonomou, M. G.; Rayne, S.; Fischer, M.; Fernandez, M. P.; Cretney, W. Chemosphere 2002 , 46, 649-663. (6) Hooper, K.; McDonald, T. A. Environ. Health Perspect. 2000 , 108, 387- 392. (7) Rahman, F.; Langford, K. H.; Scrimshaw, M. D.; Lester, J. N. Sci. Total Environ. 2001 , 275,1-17. (8) Alaee, M.; Sergeant, D. B.; Ikonomou, M. G.; Luross, J. M. Chemosphere 2001 , 44, 1489-1495. (9) Thomsen, C.; Lundanes, E.; Becher, G. J. Sep. Sci. 2001 , 24, 282-290. (10) Haglund, P. S.; Zook, D. R.; Buser, H. R.; Hu, J. W. Environ. Sci. Technol. 1997 , 31, 3281-3287. (11) Eljarrat, E.; Lacorte, S.; Barcelo, D. J. Mass Spectrom. 2002 , 37, 76-84. Anal. Chem. 2002, 74, 5263-5272 10.1021/ac020191j CCC: $22.00 © 2002 American Chemical Society Analytical Chemistry, Vol. 74, No. 20, October 15, 2002 5263 Published on Web 09/11/2002