A gas chromatography/high-resolution mass spectrometry GC/HRMS) method for determination of polybrominated diphenyl ethers in sh

Transcription

1 Chemosphere ) 1489± A gas chromatography/high-resolution mass spectrometry GC/HRMS) method for determination of polybrominated diphenyl ethers in sh M.Alaee a, *, D.B. Sergeant b, M.G. Ikonomou c, J.M. Luross b a Aquatic Ecosystem Conservation Branch, National Water Research Institute, Environment Canada, P.O. Box 5050, 867 Lakeshore Road, Burlington, Ont., Canada L7R 4A6 b Great Lakes Laboratory for Fisheries and Aquatic Sciences, Fisheries and Oceans Canada, 867 Lakeshore Road, Burlington, Ont., Canada L7R 4A6 c Contaminants Science Section, Institute for Ocean Sciences, Fisheries and Oceans Canada, P.O. Box 6000, 9860 West Sanich Road, Sidney, BC, Canada V8L 4B2 Received 2 February 2000; received in revised form 11 April 2000; accepted 20 July 2000 Abstract A method for the determination of polybrominated diphenyl ethers PBDEs) in biota for routine analysis is described.the mass spectroscopic MS) evaluation of 23 brominated diphenyl ethers, under electron ionization and electron capture negative ion conditions using magnetic sector and quadrupole mass spectrometers, showed that highresolution mass spectrometry HRMS) under electron ionization conditions was the most reliable technique, with high selectivity and adequate sensitivity.the instrument detection limit for this method ranged for individual congeners between 4.8 and 0.1 pg for 3-bromodiphenyl ether BDE-2) and 2,3 0,4,4 0 -tetrabromodiphenyl ether BDE-66), respectively, and method detection limit for each homologue group ranged between 5 pg/g for salmon certi ed reference material CRM) and 93 pg/g for lake trout CRM. The e ectiveness of this method was evaluated by analyzing the occurrence of PBDEs in commercially available CRMs comprising Lake Ontario lake trout, Paci c herring, and sockeye salmon.the average coe cients of variation for the replicate analyses of PDBEs in several tissue samples were: 25% for lake trout, 36% for Paci c herring, and 34% for sockeye salmon.the average deviations in the inter-laboratory study were: 14% for lake trout, 15% for Paci c herring, and 37% for sockeye salmon.results indicated that the described method, based on gas chromatography/highresolution mass spectrometry, is reliable for determining PBDE concentrations in biological tissues. Ó 2001 Elsevier Science Ltd.All rights reserved. Keywords: Polybrominated diphenyl ethers; Brominated ame retardants; Fish certi ed reference material; GC/HRMS 1. Introduction Polybrominated diphenyl ethers PBDEs) are ameretardant chemicals that are added to manufactured * Corresponding author.fax: address: mehran.alaee@cciw.ca M. Alaee). products including paints, plastics, and textiles van Esch, 1994); as such, they can be released into the environment when the products containing PBDEs are discarded Hutzinger et al., 1976; Hutzinger and Thoma, 1987).The annual global production of PBDE in 1992 was tons, and it continues to grow van Esch, 1994).The extensive use of products containing PBDEs has resulted in the release of these compounds into the /01/$ - see front matter Ó 2001 Elsevier Science Ltd.All rights reserved. PII: S )

2 1490 M. Alaee et al. / Chemosphere ) 1489±1495 environment.pbdes are lipophilic compounds and are shown to bio-accumulate through the food web Sellstrom et al., 1993). In 1979, the presence of BDE-209 deca-bde) in soil and sludge was detected in the areas surrounding plants where PBDEs were manufactured in the US DeCarlo, 1979).Two years later, Andersson and Blomkvist 1981) reported the presence of PBDEs in samples collected along the Viskan River in Sweden.Jansson et al. 1987) rst indicated that PBDEs are global contaminants by demonstrating the presence of PBDEs in the pectoral muscle tissue of sh-eating birds and in the blubber of marine mammals collected from the Baltic Sea, North Sea and Arctic Ocean.PBDE congeners were also observed in marine sh, shell sh, sediments Watanabe et al., 1987) and air particulates from Japan and Taiwan Watanabe et al., 1992). PBDEs were also reported in cod liver and herring from the North Sea de Boer, 1989), and in eels from fresh water systems in The Netherlands de Boer, 1990).Sta ord 1983) reported the presence of PBDEs in eggs and tissues of sh-eating birds from six states in the US and from Ontario, Canada.Stanley et al. 1991) reported the presence of PBDEs in human adipose tissue.noren and Meironyte 1998) found PBDEs in human milk and determined that the amount has been increasing over the past 25 years with concentrations doubling every ve years. In order to evaluate the global distribution, movement and fate of PBDEs in the environment, a sensitive, comprehensive, and interference-free analytical method is required for their determination in complex environmental matrices.a number of procedures for the determination of PBDEs in the environment have been reported.van Esch 1994) has provided a comprehensive review of the analytical methods used for the determination of PBDEs in the environment.the majority of the methods are based on extraction with a hydrophobic solvent followed by fractionation using normal phase chromatography, and detection using gas chromatography with electron capture detection ECD) and/or mass spectrometry MS) Andersson and Blomkvist, 1981; Kaart and Kokk, 1987; Watanabe et al., 1987). Even though ECD is a sensitive detector, it lacks selectivity.gc/ms in ECNI mode Kuger, 1988; Jansson et al., 1991) has comparable sensitivity to ECD. The ECNI spectra of most brominated compounds, including PBDEs, are dominated by masses 79 and 81, corresponding to Br ; as a result, the GC/ECNI/MS method is speci c to brominated compounds.the EI spectra of PBDEs are dominated by M±Br 2 and M, which are speci c to homologue groups of PBDEs.GC/ EI/MS analysis based on quadrupole mass spectrometers shows adequate sensitivity only for the analysis of lower brominated homologue groups.high molecular weight PBDEs are out of the mass range of most quadrupole mass spectrometers.magnetic-sector-based GC/MS systems are the most ideal instruments for this type of analysis Cramer et al., 1990). With the anticipation that a number of laboratories in the government, private sector, and academia) will engage in PBDE analysis, there is a need to establish a robust method for routine analysis of PBDEs, along with appropriate quality assurance/quality control QA/ QC).The initial step of this study was to develop a reliable, sensitive, speci c and transferable method for routine determination of PBDEs in biota samples. Since reference materials RMs) and certi ed reference materials CRMs) are essential components of QA/ QC programs, there is a need to develop such materials for PBDEs.In 1992±1993, three CRMs based on sh tissue Lake Ontario lake trout, Paci c herring and sockeye salmon) were produced for PCDD, PCDF, and co-planar PCB determinations Sergeant and Bolt, 1997).As part of this study, the feasibility of these tissue samples were evaluated as the basis to develop CRMs for future round-robin studies of PBDEs. 2. Experimental 2.1. Materials Custom standard solutions were purchased from Cambridge Isotope Laboratories Andover, MA), and consisted of analytical, surrogate spiking, and performance standards.cil also provided individual standard solutions for the purpose of checking PBDE purity for individual congeners and determining relative retention times.anhydrous granular sodium sulfate reagent grade, dichloromethane distilled in glass and chromatography grade hexane were acquired from Caledon Laboratories Georgetown, Ont.) Extraction and cleanup Homogenates of whole sh CRMs CIL) in ampoules were vortexed to re-suspend the tissue and lipids.a 10 g aliquot of the homogenate was transferred quantitatively to large mortars and 130 g of anhydrous Na 2 SO 4 was added.the sample mixture was ground manually until a free- owing mixture resulted.this mixture was transferred into a 300 mm 45 mm o.d. chromatography column and was spiked directly on the homogenate with 20 ll of the surrogate mixture containing 20±60 pg=ll 13 C 12 tetra- through octa-chlorodiphenyl ethers CDPEs) Cambridge Isotope Laboratories EO- 4150).The column bed was eluted with 300 ml of dichloromethane DCM).Samples were concentrated by a combination of rotary evaporation and nitrogen evaporation prior to gel permeation chromatography GPC). The GPC unit was an automated ABC Laboratories Autoprep model 1002A.The column was packed with

3 M. Alaee et al. / Chemosphere ) 1489± g of Bio Beads S-X3, 200±400 mesh Bio-Rad Laboratories, Richmond, CA) in a 253-mm 600-mm glass column.the elution solvent was 300 ml of DCM:hexane 1:1).Fractionation was accomplished with 10 g of 3% deactivated silica gel 100±200 l) columns 250 mm 10 mm i.d.), eluted with 140 ml of DCM. The solvent was allowed to evaporate to dryness at room temperature to minimize losses and 20 ll of performance standard 100 pg=ll 13 C 12 hexa-cdpe and tetra-pbde) was added before analysis Instrumental analysis Preliminary determination of the spectroscopic characteristics of PBDEs was accomplished using a Hewlett±Packard 5973 GC/MS under EI and ECNI conditions.the MS was connected to a Hewlett±Packard 6890 GC with a 7683 autosampler.the GC was equipped with a split±splitless injector held constant at 250 C.Gas chromatographic separations were achieved using a 30-m HP-5 column.the GC column was maintained at 110 C for 1 min, then ramped at 15 C/ min to 180 C, further ramped at 2 C= min to 280 C and held at this temperature for 10 min.the total run time was 60.0 min. The transfer line was held constant at 250 C.In EI mode, the MS source temperature was 250 C, and the electron energy was 70 ev.under ECNI conditions, the source temperature was kept at 150 C. Methane 2.2 ml/min was used as the moderating gas and uorether E-3 2H-per uoro-5,8-dimethyl-3,6,9-trioxaundecane) was used as the calibration gas.the instrument was scanned from 75 to 750 at 1.2 s/scan. High-resolution GC/MS analyses of PBDEs were carried out on a VG AutoSpec-Q mass spectrometer connected to a Hewlett±Packard 5890 GC equipped with a CTC A200s autosampler.the GC injection port was con gured for 1 ll on-column injections, with an initial temperature of 110 C, held for 1 min, and ramped at 100 C= min to 280 C, and held at this temperature for 55 min.gas chromatographic separation prior to MS was achieved using a 60 m 0.25 mm 0.25 lm Restek RTX-5 capillary column.the GC conditions were the same as above, with the exception of the nal hold being extended to 60 min.the total run time was 90.7 min. Ionization was performed by electron ionization EI) at an electron voltage ranging from 30 to 40 ev depending on the optimization parameters of the instrument.the source temperature was 270 C, and the resolving power of the analyzer was The mass spectrometer was operated in selected ion monitoring SIM) mode using eight descriptors to analyze the 23 PBDE congeners Table 1).Quanti cation of the samples was performed using an internal standard method incorporating Excel and 20/20 spreadsheets, and following EPA 1613 QA/ QC protocols US EPA, 1990).The elution orders of PBDEs were also evaluated using a 60 m 0.25 mm 0.25 lm DB1701.The identities and concentrations of PBDEs were compared to the results obtained using the RTX-5 column for selected samples n ˆ 25. The di erences in the concentrations of homologue groups between two columns were less than 10%. Table 1 PBDE experimental conditions for HRMS Function PBDE Ion Mass PFK lock mass Surrogate compound 13 C±CDE 1 Mono M ± ± ± Di M ± ± ± Tri M ,3 0,4, M Tetra M±Br ,3,3 0,4, M ,2 0,3,3 0,4, ,3,3 0,4,4 0, M±Cl 2 5 Tetra M C-3,3 0,4,4 0 -BDE M Penta M±Br ,2 0,3,3 0,4,4 0, M±Cl 2 2,2 0,3,3 0,4,4 0,5, M±Cl 2 7 Hexa M±Br ± ± ± Hepta M±Br ± ± ± Mass Ion

4 1492 M. Alaee et al. / Chemosphere ) 1489± Results and discussion Mass spectroscopic characteristics of the 23 PBDEs are summarized in Table 2.ECNI spectra of the 23 PBDEs were dominated by m/e 79 and 81, corresponding to Br, and, to a lesser extent, m/e 159, 161, 163, corresponding to HBr 2.In EI mode, the spectra for PBDEs were dominated by M, and M-160) indicating that the formation of odd-electron species was favored.the presence of ortho-br favored the formation of M±Br 2 over M ; Marsh et al. 1999) reported similar results.the EI mass spectra of polychlorinated diphenyl ethers resembled those of PBDEs and were dominated by M and M-70) corresponding to M±Cl 2 Alaee et al., 1999). The most predominant and characteristic ion clusters for each of the congeners were selected for the SIM window Table 1).For mono-pbde through tri-pbde, the M ions were selected.for the rest of the homologue groups tetra- through hepta-pbde), M±Br 2 ions were selected.one exception to this pattern was 3,3 0,4, 4 0 -tetrabromodiphenyl ether, which had predominant ion clusters at the M.The elution order of the 23 PBDEs was determined from individual standards.the retention times for these eight functions were veri ed using a single-function program containing a single ion from each homologue group at m=dm ˆ 5000.The single-function program was also used to determine if any potential PBDEs were not included in the current windows. HRGC/HRMS in EI mode provided the most selective method and reasonable sensitivity for the determination of PBDEs.Since only 23 congeners out of 209 were commercially available, it was decided that a method based on the EPA 1613 analytical procedure would provide information not only on the selected congeners, but also on the presence of other congeners, and would allow the estimation of their concentrations based on average response factors.consequently a method based on HRGC/HRMS was developed for the determination of congener-speci c brominated diphenyl ether PBDE) compounds in biota samples.since only one 13 C-labeled PBDE 13 C 12 3,3 0,4,4 0 -tetra-bde) was commercially available, and was already being used as the performance standard, 13 C-labeled PCDEs tetra± octa) were used as the internal standards.the recoveries for the internal standards ranged between 65% and 120%.Average method detection limits MDLs) varied between 5 and 93 pg/g.the average CVs for the replicate analysis of PBDEs in CRM tissue samples n ˆ 7 were: 25% for lake trout, 36% for Paci c herring, and 34% for sockeye salmon. Table 2 Base peak and secondary ions along with fragment of 23 congeners of PBDEs used in this study PBDE Congener Electron ionization Electron capture negative ion # Structure Base peak m/e) Secondary peak m/e) Base peak m/e) Secondary peak m/e) 1 2-mono 169, M±Br) 248, 250, M 79, 81, Br 161, HBr mono 248, 250, M 141, M±CBrO) 79, 81, Br 161, HBr 2 7 2,4-di 168, M±Br 2 328, M 79, 81, Br 161, HBr 2 8 2,4 0 -di 168, M±Br 2 328, M 79, 81, Br 161, HBr ,6-di 168, M±Br 2 328, M 79, 81, Br ± 12 3,4-di 328, M 168, M±Br 2 79, 81, Br ± 13 3,4 0 -di 328, M 168, M±Br 2 79, 81, Br 161; HBr ,4 0 -di 328, M 168, M±Br 2 79, 81, Br ± 30 2,4,6-tri 246, 248, M±Br 2 406, 408, M 79, 81, Br 161, HBr ,4 0,6-tri 246, 248, M±Br 2 406, 408, M 79, 81, Br 161, HBr ,3,4-tri 246, 248, M±Br 2 406, 408, M 79, 81, Br 161, HBr ,3 0,4-tri 406, 408, M 246, 248, M±Br 2 79, 81, Br 161, HBr ,4,4 0 -tri 406, 408, M 246, 248, M±Br 2 79, 81, Br ± 47 2,2 0,4,4 0 -tetra 326, M±Br 2 486, M 79, 81, Br ± 66 2,3 0,4,4 0 -tetra 326, M±Br 2 486, M 79, 81, Br 161, HBr ,3 0,4 0,6-tetra 326, M±Br 2 486, M 79, 81, Br 161, HBr ,3 0,4,4 0 -tetra 486, M 326, M±Br 2 79, 81, Br 161, HBr ,4,4 0,6-tetra 326, M±Br 2 486, M 79, 81, Br 161, HBr ,2 0,3,4,4 0 -penta 406, 408, M±Br 2 564, 566, M 79, 81, Br ± 99 2,2 0,4,4 0,5-penta 406, 408, M±Br 2 564, 566, M 79, 81, Br 161, HBr ,3 0,4,4 0,6-penta 406, 408, M±Br 2 564, 566, M 79, 81, Br 161, HBr ,2 0,4,4 0,5,5 0 -hexa 484, M±Br a,m 79, 81, Br 161, HBr ,3,3 0,4,4 0,5,6-hepta 562, M±Br a, 723 a,m 79, 81, Br 161, HBr 2 a Exact mass for hexa-bde ˆ and hepta BDE ˆ and ; odd masses were detected because of bromine mass de ciency results are within experimental error of quadrupole MS).

5 M. Alaee et al. / Chemosphere ) 1489± Fig.1.Total ion current TIC) of BDPE congeners with 13 C CDPEs used as internal standard a) and in Lake Ontario lake trout b). In this gure, each function was normalized to 100% to illustrate the presence of various homologue groups and does not show the relative abundance of PBDEs in the lake trout sample. Experimental results in the form of total ion chromatograms of the 23-congener standards and those found in Lake Ontario lake trout are presented in Fig.1. The number of congeners in the standard was not suf- cient to match all of the congeners in the sample; consequently, an average response factor was used to estimate the concentrations of each homologue group. The concentration of PBDEs in Lake Ontario lake trout, Paci c herring and sockeye salmon are presented in Fig. 2.Lake Ontario lake trout had higher levels of PBDEs than Paci c herring and sockeye salmon.the higher concentrations of the PBDEs in the lake trout can be attributed to the di erences in their habitat and to their position at the top of the food web; they represent a naturally contaminated sample.paci c herring were collected from the northern tip of Vancouver Island; they represent a relatively uncontaminated sample. Sockeye salmon also represent a relatively uncontaminated sample suitable for spiking.the trends in the concentrations of PBDEs in the CRMs were similar to those of other organohalogen compounds reported in a previous inter-laboratory study Sergeant and Bolt, 1997). Among the homologue groups present in the 23- congener standard di±hepta), tetra- and penta-brominated diphenyl ether homologues were the predominant homologue groups in the CRMs.The main congener in the tetra homologue group was 2,2 0,4,4 0 -tetra-bde BDE-47), which was observed in all Lake Ontario lake Fig.2.Distribution of PBDE homologue groups in sh CRMs. trout and Paci c herring samples, followed by 2,2 0,4,4 0,5-penta-BDE BDE-99).These same congeners were also found in Baltic herring and gray and ringed seals, as well as osprey in Sweden Jansson et al., 1993). Andersson and Blomkvist 1981) also found high levels of 2,2 0,4,4 0 -tetra-pbde in pike from Swedish waters. In order to validate this method, a subset of the same samples lake trout, herring, and sockeye salmon) were

6 1494 M. Alaee et al. / Chemosphere ) 1489±1495 Table 3 Concentration of PBDEs in Lake Ontario lake trout, Paci c herring, and sockeye salmon CRMs, determined at CCIW and IOS Homologue group CCIW pg/g) IOS pg/g) Ave. pg/g) % CV Lake trout Lipid ˆ 7.97%) n ˆ 7) n ˆ 3) di tri tetra penta hexa hepta Average: 14 Herring Lipid ˆ 3.75%) n ˆ 4) n ˆ 3) di nd a nd a ± ± tri tetra penta hexa hepta Average: 15 Sockeye salmon Lipid ˆ 4.16%) n ˆ 6) n ˆ 1) di nd a nd a ± ± tri 4 nd a ± ± tetra penta hexa hepta Average: 37 a nd ˆ not detected. analyzed at the Institute of Ocean Sciences IOS).The method used at IOS was similar to the one described above, with the exception of using an additional alumina column followed by a carbon column clean-up Ikonomou et al., 1999). In general, the agreement between the two laboratories was very good.results from this interlaboratory study are presented in Table 3.The average deviation of 14%, 15% and 37% for lake trout, herring, and salmon are smaller than the experimental range for the replicate samples reported above, and are similar to the values reported for PCB, PCDD, PCDF and organochlorine pesticides in other inter-laboratory studies Sergeant and Bolt, 1997).The higher inter-laboratory deviation for sockeye salmon was attributed to the lower concentration of PBDEs in these samples. 4. Conclusions A reliable and sensitive method based on HRGC/ HRMS has been developed for the determination of PBDE concentrations in biota.this method has been successfully applied by Luross et al. 1998) to the study of PBDEs in lake trout from the Great Lakes.This method is based on the 23 congeners that are commercially available.additional 13 C-labeled PBDEs, along with more congener standards, will enhance the reliability of this method.the long retention times for GC analysis, which uses conventional capillary columns, can be addressed with fast GC and/or application of hightemperature columns. Signi cant levels of PBDEs were found in both Lake Ontario lake trout, and Paci c herring, whereas lesser quantities of PBDEs are present in sockeye salmon.the presence of PBDEs in these CRMs makes them a valuable tool for QA/QC and method validation.a formal round-robin exercise would increase the con dence in the reported results. Acknowledgements The authors would like to acknowledge the Department of Fisheries and Oceans, Canada, for funding this project under the Toxic Chemicals Program.We also thank CIL for providing individual standards of the 23 PBDE congeners.the authors acknowledge technical support provided by R.Wilkinson, N.Crewe, and T.He during these experiments, and editorial comments provided by M.Fischer.

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