Environ. Sci. Technol. 2007, 41, 1554-1559
Spatial Distribution of Perfluoroalkyl Contaminants in Lake Trout from the Great Lakes VASILE I. FURDUI,† NAOMI L. STOCK,† DAVID A. ELLIS,† CRAIG M. BUTT,† D. MICHAEL WHITTLE,‡ PATRICK W. CROZIER,§ ERIC J. REINER,§ DEREK C. G. MUIR,⊥ AND S C O T T A . M A B U R Y * ,† Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, M5S 3H6, Department of Fisheries & Oceans, Great Lakes Laboratory for Fisheries and Aquatic Sciences, 867 Lakeshore Road, Burlington, Ontario, L7R 4A6, Ontario Ministry of the Environment, Laboratory Services Branch, 125 Resources Road, Etobicoke, Ontario, M9P 3V6, and Water Science and Technology Directorate, Environment Canada, 867 Lakeshore Road, Burlington, Ontario, L7R 4A6
Individual whole body homogenates of 4 year old lake trout (Salvelinus namaycush) samples collected in 2001 from each of the Great Lakes were extracted using a novel fluorophilicity cleanup step and analyzed for perfluoroalkyl compounds (PFCs). Standard addition and internal standardization were used for quantification. Results were reported (( SE) for perfluorinated carboxylates (PFCAs), perfluorinated sulfonates (PFSAs), and unsaturated fluorotelomer carboxylates (8:2 and 10:2 FTUCA). The lowest average concentration of ∑PFC was found in samples from Lake Superior (13 ( 1 ng g-1), while the highest average concentration was found in samples from Lake Erie (152 ( 14 ng g-1). Samples from Lake Ontario (60 ( 5 ng g-1) and Lake Huron (58 ( 10 ng g-1) showed similar average ∑PFC concentrations, although the perfluorinated sulfonate/carboxylate ratios were different. The major perfluoroalkyl contaminant observed was perfluorooctane sulfonate (PFOS) with the highest concentration found in samples from Lake Erie (121 ( 14 ng g-1), followed by samples from Lake Ontario (46 ( 5 ng g-1), Lake Huron (39 ( 10 ng g-1), Lake Michigan (16 ( 3 ng g-1), and Lake Superior (5 ( 1 ng g-1). Perfluorodecane sulfonate (PFDS) was detected in 89% of the samples, with the highest concentration in Lake Erie samples (9.8 ( 1.6 ng g-1), and lowest concentration in samples from Lake Superior (0.7 ( 0.1 ng g-1). Statistically significant correlations were observed between PFOS and PFDS concentrations, and PFOS concentration and body weight, respectively. The PFCAs were detected in all samples, with the highest total average concentration in samples from Lake Erie (19 ng g-1), followed by samples from Lake Huron (16 ng g-1), Lake Ontario (10 ng g-1), Lake Michigan (9 ng g-1) and Lake Superior (7 ng g-1). The compounds with significant contributions to the ∑PFCA concentrations were PFOA * Corresponding author phone/fax: (416) 978-3596; e-mail:
[email protected]. † University of Toronto. ‡ Great Lakes Laboratory for Fisheries and Aquatic Sciences. § Ontario Ministry of the Environment. ⊥ Environment Canada. 1554
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and C9-C13-PFCAs. The 8:2 FTUCA was detected at concentrations ranging between 0.1 and 0.2 ng g-1, with the highest level in samples showing also elevated concentrations of PFOA (4.4 ng g-1 for Lake Michigan vs 1.5 ng g-1 for all other samples). The 10:2 FTUCA was detected only in 9% of all samples (nd, 45 pg g-1). For those PFCs where we determined lake water concentrations, the highest log BAFs were calculated for PFOS (4.1), PFDA (3.9), and PFOSA (3.8).
Introduction Perfluoroalkyl compounds (PFCs), including perfluorocarboxylates (CF3(CF2)nCOO-, PFCAs) and perfluorosulfonates (CF3(CF2)nSO-3, PFSAs), have a variety of consumer, commercial, and industrial applications. These include fluorosurfactants and fluorinated polymers (1), polymerization aids in fluoropolymer manufacturing (2) for PFCAs, and firefighting foams (3) for PFSAs. As a result of their widespread use and persistent nature, PFCs are currently being detected globally in the environment (4), humans (5), and wildlife (6), including those from remote locations (7). Sources of PFCs to the environment have not been completely characterized. Perfluorooctane sulfonate (PFOS) and other perfluorosulfonates have been released to the environment directly through uses such as aqueous firefighting foams, or indirectly through either abiotic (8, 9) and/ or biotic (10, 11) degradation of precursor molecules such as the polyfluorinated sulfonamides (CF3(CF2)nSO2NR1R2). Despite a manufacturing phase-out of all C8 sulfonyl chemistry by 2002, sulfonamides are still present in the atmosphere, and degradation of these contaminants is a continuing source of PFOS to the environment (12, 13). Perfluorooctanoic acid (PFOA) and other long-chain PFCAs, currently in use, may enter the environment directly (14). In addition, fluorotelomer alcohols (CF3(CF2)nCH2CH2OH) have been shown to degrade biotically (15-18) and abiotically, in both the atmospheric (8, 19) and aquatic environments (20), to produce PFCAs. The first report of PFCs in biota was published in 2001, when PFOS was identified as a bioaccumulative pollutant in fish and wildlife (6). The observation of long chain PFCAs in fish were reported for the first time in 2002 (4). Since then both PFCAs and PFSAs have been detected in fish from the Baltic and Mediterranean Seas (21), the Japanese Coast (22), Lake Ontario (23), the Canadian Arctic (7), and the southeastern coast of the U.S. (24). Recently, fish have also been identified as a source of PFCs in humans living on the Baltic coast (25). As such, a greater understanding of the environmental behavior of perfluorinated surfactants in fish is required. Previous analysis of PFCs in biota, typically involved limited cleanup for removing lipids during sample extraction (26), increasing the potential for matrix interference during analysis. It has long been known that highly fluorinated species show greatest solubility in similar highly fluorinated solvents, while non-fluorinated species show reduced solubility in these solvents (27, 28). This phenomenon, known as fluorophilicity, has been widely used in the areas of industrial synthetic and green chemistries (29, 30). It was hypothesized that the use of fluorinated solvents for the extraction of analytes of interest from biological matrices would result in a greater degree of selectivity, matrix resolution and efficiency over traditional techniques. As such, a novel fluorophilicity cleanup step, using 1,1,1,3,3,3hexafluoro-2-propanol (HFP) was developed. 10.1021/es0620484 CCC: $37.00
2007 American Chemical Society Published on Web 01/20/2007
In this study, lake trout from the Great Lakes were analyzed for a suite of PFCAs, PFSAs, and fluorotelomer carboxylic acids (FTCAs). The unique nature of this sample set, all lake trout being identically aged, allows for determination of spatial trends and calculation of bioaccumulation factors (BAFs).
Experimental Section Standards and Chemicals. Potassium perfluorohexane sulfonate (PFHxS, 99.9%), potassium PFOS (86.4%) and heptadecafluorooctane sulfonamide (PFOSA, 99.9%) were provided by the 3M Company (St Paul, MN). Standards of perfluoroheptanoic acid (PFHpA, 99%), PFOA (96%), perfluorononanoic acid (PFNA, 97%), perfluorodecanoic acid (PFDA, 98%), perfluoroundecanoic acid (PFUnA, 95%), perfluorododecanoic acid (PFDoA, 95%), perfluorotetradecanoic acid (PFTeA 97%), potassium PFDS (25%), HFP, and tetrabutylammonium hydrogensulfate (TBAS) were purchased from Sigma-Aldrich (Oakville, ON, Canada). Optima grade methanol (MeOH) and HPLC grade water were purchased from Fisher Scientific (Toronto, ON, Canada) and methyl-tert-butyl ether (MTBE) from Caledon Laboratories Ltd. (Geogetown, ON, Canada). Standards of the fluorotelomer acids (6:2, 8:2 and 10:2) were obtained from Wellington Laboratories (Guelph, ON, Canada). Mass-labeled (13C) perfluorocarboxylic acids (13C4-PFOA, 13C -PFNA and 13C -PFDA), unsaturated fluorotelomer acids 5 2 (13C2-6:2 FTUCA, 13C2-8:2 FTUCA and 13C2-10:2 FTUCA) and a sulfonate (13C4-PFOS) were obtained from Wellington Laboratories (Guelph, ON, Canada); 13C2-PFOA was obtained from Perkin-Elmer Life Sciences (Boston, MA). Sample Preparation. Lake trout samples of the same age class (4 years) were collected in 2001 from Lake Superior (n ) 10), Lake Michigan (n ) 10), Lake Huron (n ) 10), Lake Erie (n ) 6) and Lake Ontario (n ) 10). Samples selected ranged between 42 and 62 cm length and 663-2896 g weight (Table S1, Supporting Information). Nylon gillnets with stretched mesh sizes of 7.5 - 11.5 cm (equivalent to commercial mesh sizes of 3.0-4.5 in.) were used for overnight collections in 30 to 40 m of water at various locations in the Great Lakes. All lake trout samples were processed as individual whole fish homogenates and then stored in the Great Lakes Fisheries Specimen Bank at -80 °C in sealed glass containers with plastic caps lined with clean aluminum foil (i.e., rinsed with pesticide grade acetone and hexane). Fish sample homogenates were thawed at room temperature, stirred, and subsampled in polyethylene vials (4-5 g). The ion pairing method from Hansen et al. (5) was used with some modifications. Approximately 0.4 g of each homogenate was weighed and placed in 15 mL plastic centrifuge tubes (polypropylene copolymer) with 4 mL Na2CO3 (0.25 M) and 0.5 mL of the ion-pairing agent TBAS (0.5M adjusted to pH 10 with 8 M NaOH). Procedural blanks (n ) 11) were prepared using HPLC grade water and five samples were spiked with 10 ng of each analyte for recovery calculation. Samples were further homogenized using a Tissue Tearor homogenizer (Biospec Products Inc., Bartlesville, OK). The resulting homogenates were mixed with 5 mL of MTBE, shaken vigorously for 5 min, and centrifuged to separate the supernatant (MTBE). For each sample the MTBE extract was collected in a separate plastic tube, the MTBE extraction process repeated once more. The MTBE supernatants (10 mL) were combined, reduced to ∼0.5 mL using high purity N2 gas, then mixed with ∼0.5 mL of HFP, shaken vigorously for 1 min, and centrifuged for 10 min. The precipitated lipids, protein, and other coextractables were removed using 0.2 µm nylon filters, while the target analytes remained soluble in the solvent mixture. Full details on the development of the fluorophilicity cleanup step are available in the Supporting Information (Discussion and Table S3).
The filtrates were blown to dryness using high purity N2 gas and the residue was reconstituted in 1 mL of 100% MeOH containing 13C4-PFOA (2 ng) control standard. The final extracts were filtered through 0.2 µm nylon filters and stored in polypropylene vials at -20 °C until analysis. Multiple dilutions of the final extracts (1:10, 1:50, 1:1000) were analyzed. Final extracts were mixed with MeOH, internal standards (13C2-PFOA, 13C5-PFNA, 13C2-PFDA, 13C4-PFOS, 13 C2- 6:2, 8:2, and 10:2 FTUCA) in MeOH and HPLC grade water (50% final concentration) for injection. The sample/ MeOH injection mixtures were filtered using Mini-UniPrep syringeless filter devices having 0.2 µm polypropylene (PP) filter media and PP housings (Whatman, Florham Park, NJ). Instrumental Analysis by LC/MS/MS. Analysis of target analytes was performed using a high performance liquid chromatograph-tandem mass spectrometer system (HPLCMS/MS), consisting of an unmodified Agilent 1100 Series liquid chromatograph coupled with a 4000 QTRAP triple quadrupole mass spectrometer (Applied BiosystemssMDS Sciex, Concord, ON, Canada). Water and MeOH solvents (0.01 M ammonium acetate) were delivered at a total flow rate of 250 µL min-1. One hundred microliter aliquots of the sample/ MeOH mixtures were injected through a C18 guard column (2 mm i.d. × 4 mm, Phenomenex, Torrance, CA) with chromatographic separation performed on a Genesis C18 column (2.1 mm i.d. × 50 mm, 4 µm; Chromatographic Specialties, Brockville, ON, Canada). Target analyte separation was obtained in 8 min under gradient conditions, with 75:25 MeOH /water initial mobile phase, followed immediately by 3 min ramp to 90:10 MeOH /water, a 3 min hold and reverting to initial conditions at 7 min. The mass spectrometer was operated in negative electrospray ionization multiple reaction monitoring (MRM) mode. Mass spectrometer source/gas (N2) related parameters were ion spray voltage at -4500 V, turbo ion spray 60 psi at 400 °C, nebulizer gas 45 psi, curtain gas 10 psi, interface heater 100 °C and collision gas 3 × 10-5 Torr. MRM transition related parameters were optimized for each analyte, monitoring SO3F- (m/z ) 99) for sulfonates, SO2N- (m/z ) 78) for PFOSA, a loss of CO2 for carboxylates, and a loss of CO2 + HF for the unsaturated fluorotelomer acids (Table S2, Supporting Information). Quantification was performed using both internal standard (IS) and standard addition (SA) methods to allow the intercalibration of the two methods and determine the importance of potential matrix effects. Solvent matched standard mixtures containing 5, 10, 20, 50, 100, 200, 500, and 1000 ng L-1 were used to create calibration curves for each analyte. Concentrations were not adjusted for standard purities. Since no standard was available for PFTrA, a calibration curve was obtained by averaging the peak areas of PFDoA and PFTeA obtained for different concentrations. Perfluoropentadecanoic acid (PFPA) was quantified using the calibration curve obtained for PFTeA. Isotope dilution was used to quantify PFOS (13C4-PFOS), PFOA (13C2-PFOA), PFNA (13C5-PFNA), PFDA (13C2-PFDA), 8:2 FTUCA (13C2-8:2 FTUCA), and 10:2 FTUCA (13C2-10:2 FTUCA). Based on chromatographic retention times, peak area counts for PFHxS and PFHpA were corrected based on the 13C2-PFOA internal standard response, while PFOSA, PFUnA, PFDoA, PFTrA, PFTeA, and PFPA were corrected based on the 13C2-PFDA internal standard response. One replicate was analyzed for each sample, with three injections per replicate. Duplicate samples were analyzed separately (n ) 10) and 15 samples (n ) 18 for PFOS) were quantified using the standard addition method, with three standard additions (50, 100, and 200% of analyte concentration, considering corresponding dilutions of the extracts). Mean recovery of each target analyte was greater than 65% (Table S4, Supporting Information), except PFOSA (44%). VOL. 41, NO. 5, 2007 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 1. Mean Concentrations (ng g-1 Wet Weight ( Standard Error (SE) of the Mean) of Contaminants in Whole Body Homogenates of Lake Trout Collected from the Great Lakes in 2001a analyte 8:2 FTUCA 10:2 FTUCA PFHpA PFOA PFNA PFDA PFUnA PFDoA PFTrA PFTeA PFPA ∑PFCA PFHxS PFOS PFDS PFOSA ∑PFSA ∑PFSA/∑PFCA
chemical formula -
CF3(CF2)6CFdCHCO2 CF3(CF2)8CFdCHCO2CF3(CF2)5CO2CF3(CF2)6CO2CF3(CF2)7CO2CF3(CF2)8CO2CF3(CF2)9CO2CF3(CF2)10CO2CF3(CF2)11CO2CF3(CF2)12CO2CF3(CF2)13CO2CF3(CF2)5SO3CF3(CF2)7SO3CF3(CF2)9SO3CF3(CF2)7SO2NH2
Lake Superior
Lake Michigan
Lake Huron
Lake Erie
Lake Ontario
