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Environmental Measurements Methods
In-Vial Extraction Large Volume Gas Chromatography Mass Spectrometry for Analysis of Volatile PFASs in Papers and Textiles Justin Rewerts, Jeffrey T Morre, Staci Massey-Simonich, and Jennifer A. Field Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.8b04304 • Publication Date (Web): 27 Aug 2018 Downloaded from http://pubs.acs.org on September 5, 2018
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In-Vial Extraction Large Volume Gas Chromatography Mass Spectrometry for Analysis of Volatile PFASs on Papers and Textiles
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Justin N. Rewerts,a Jeffrey T. Morré,a Staci L. Massey Simonich,b and Jennifer A. Fielda,b*
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a,
Department of Chemistry, 153 Gilbert Hall, Oregon State University, Corvallis, Oregon 97331,
[email protected],
[email protected] b Department of Environmental and Molecular Toxicology 1007 ALS Bldg., 2750 Campus Way, Oregon State University, Corvallis, OR, 97331,
[email protected],
[email protected] *Corresponding Author
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Keywords: PFASs, volatile PFASs, FTOHs, FOSE, perfluorinated, polyfluorinated, paper, textiles, consumer products, GC-MS, GC-LVI, CSR-LVSI. GC-QTOF
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TOC Art
Extraction + GC Analysis 99% purity,
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HPLC grade) was purchased from Fisher Scientific (Hampton, New Hampshire). 5 ACS Paragon Plus Environment
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Sample collection and storage
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For the purpose of method demonstration, seven papers and nine textiles were selected as samples of
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convenience. The seven papers consisted of all new materials purchased or acquired in 2017, including:
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white copier paper, five food-contact materials, and waterproof notebook paper (Table 2). Washington
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State Department of Ecology (WSDOE) provided one of the food contact papers (Paper 3) which was also
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used in a previous study4. The nine textiles consisted of: a plain white t-shirt, three office chair
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upholsteries from the years 1988a, 1988b and 1993 respectively, an outdoor upholstery purchased in
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2017, two articles of previously worn children’s clothing (a swimsuit and outdoor vest), an adult rain
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jacket purchased in 2015 (provided by WSDOE), as well as a piece of a used firefighter’s jacket (Table 3).
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Trip blanks for materials purchased in 2017 consisted of white copier paper stored in quart sized Ziploc
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bags carried during sampling events. Once obtained, all samples and trip blanks were stored in separate
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Ziploc bags away from light.
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Sample Preparation and Extraction
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One square (1.5 x 1.5 cm) of each paper or textile was cut with a pair of methanol-rinsed scissors. The
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sample was also weighed and then placed into a 1.5 mL autosampler vial. Mass-labeled internal
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standards (final in-vial concentration 100 pg/µL) and methanol were added for a total volume of 1.5 mL.
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The vial was then capped and then placed into a 25°C ultrasonic bath for 30 min. The vial was then
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placed directly on the autosampler for analysis by GC-CSR-LVSI-MS, with no further cleanup or removal
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of the material from the autosampler vial.
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GC-CSR-LVSI-MS
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An Agilent 6890 GC was outfitted with a 100 µL autosampler syringe (Agilent Technologies Santa Clara,
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CA). All other GC consumables were generously donated by Restek. A 4 mm i.d. single taper Topaz inlet
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liner was used with 15 mg of deactivated quartz wool placed towards the bottom of the liner. The 6 ACS Paragon Plus Environment
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injection speed was set to 4000 µL min-1, and helium was used as the carrier gas (1.4 mL min-1, constant
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flow). For routine analysis, 20 µL splitless injections were performed using CSR-LVSI at an inlet
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temperature of 280°C. All analytes were separated using a 5 m x 0.53 mm Polar Deactivated Retention
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Gap that was connected in series to a 15 m Stabilwax analytical column (0.25 mm i.d., x 250 µm film
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thickness, Restek, Bellefonte, Pennsylvania). The retention gap-analytical column union consisted of a
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deactivated universal press-tight connector (Restek), sealed with polyamide resin (Restek). The initial
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oven temperature was held 55°C for 1.6 min, ramped to 70°C at 25°C min-1 and held for 3.4 min, and
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then ramped to 250°C at 25°C min-1, followed by a two min hold. The Agilent 6890 GC was interfaced to
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an Agilent 5973N MS detector that was operated in positive chemical ionization mode in conjunction
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with selected ion monitoring (SIM). Methane was used as the reagent gas at a flow rate of 1 mL min-1.
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Calibration and Quality Assurance
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The retention times, and ions corresponding to a molecular ion and its highest abundance fragment for
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all analytes of interest can be found in the SI (see Table S1). Analyte concentrations were determined by
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internal standard calibration and 1/x weighted linear regression of 8-point calibration curves. Calibration
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standards were made in the range of 1-2000 pg/μL for all analytes. The branched and linear isomers of
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ECF-derived analytes were integrated together as one peak for quantification purposes. A continuing
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calibration verification (CCV) was analyzed at the beginning of each analysis and was required to fall
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between 70-130% before an analytical sequence could begin. A low concentration standard was
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analyzed every eight samples to verify calibration throughout the analytical sequence (at most, 25
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samples). Additionally, both solvent blanks and method blanks were analyzed in order to track potential
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carryover or systemic contamination. Solvent blanks consisting of methanol and mass labeled internal
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standards were analyzed prior to the calibration curve, immediately after the calibration curve, and
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after every eight sample analyses. Method blanks consisted of methanol and mass labeled standards in
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an autosampler vial that were sonicated along with samples and were analyzed within an analytical 7 ACS Paragon Plus Environment
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sequence. No samples contained levels of volatile PFASs above the highest level of the calibration
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curve. As expected all solvent, method and trip blanks fell below the limit of detection (LOD) for all
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analytes.
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Data quality tier descriptions are consistent with those defined in Backe et al.34, and Allred et al35.
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Quantitative (Qn) refers to an analyte that had both a commercially available standard, and a
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corresponding mass labeled internal standard (4:2 FTOH, 6:2 FTOH, 8:2 FTOH, 10:2 FTOH, N-EtFOSA, N-
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MeFOSA, N-MeFOSE, N-EtFOSE). Screen (Sc) refers to an analyte without any commercially available
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standards (12:2 FTOH, 14:2 FTOH, all FASE homologs C2-C7). The concentrations for Sc analytes were
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estimated using the response factors of a structurally similar, Qn homologue, assuming an equal molar
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response factor. Internal standards used for Sc analytes were the closest structurally similar homolog
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(see SI).
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Optimization of LVSI
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To optimize and select the injection volume for the study, a preliminary study was conducted in which
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injections of a 100 pg/µL standard in solvent were made over a range of 1-50 µL. In order to perform
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injection in the range of 1-10 µL, a 25-µL syringe was used in conjunction with a 0.32 mm id retention
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gap. For injection ranging from 12.5-50 µL, a 100-µL syringe was employed as described above for
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routine analysis were used.
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Optimization of Extraction Conditions
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The efficiency of the extraction and total recovery of incurred (not spiked) volatile PFASs on materials
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was evaluated by varying the sonication time (30, 60 and 90 min) and temperature (25°C and 50°C) of
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the water bath. The upper end of 50°C was established to stay below the boiling point of the methanol.
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A series of experiments were carried out on three materials with four replicates for each sonication time
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and temperature treatment: Textile 5 (thin textile), Textile 7 (a fibrous, thick upholstery), and Paper 3 8 ACS Paragon Plus Environment
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(food contact material) in order to optimize extraction of incurred volatile PFASs. Paper and textile
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pieces were cut and prepared as described above. A 95% confidence interval (CI) for each set of four
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replicate treatment was calculated and used to test for statistical significance between treatments (See
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Results and Discussion).
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Method Performance
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Spike and recovery experiments were performed to compute whole method accuracy and precision.
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One blank paper (Paper 1) and one blank textile (Textile 1) with volatile PFAS that were found to have
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levels of volatile PFASs levels 0.99). For this reason, a final injection
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volume of 20 µL was selected and retention gaps were typically changed after 80 total injections, inlet
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liners were changed every 24 sample injections unless the accumulation of observable residues was
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seen on the liner. In which case, liners were changed more frequently (e.g. every 15 samples).
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Optimization of Extraction
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No statistical difference in the mass of volatile PFASs recovered was observed in the 95% CI from the
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three sample materials extracted at 25°C and 50°C with 30 min sonication (Figure S2-S4). Thus,
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independent of material type, a 25°C sonication water bath was chosen as the final temperature for the
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in-vial extraction. There was no statistical difference in the mass of PFASs recovered from the three
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sample materials at 30, 60, and 90 min of sonication at 25 °C (Figure S5-S7). For this reason, 25°C water
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bath and sonication for 30 min were used for all subsequent extractions.
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Method Performance
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Accuracy was determined by spike and recovery experiments on blank samples (Paper 1 and Textile 1).
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For Paper 1, average recovery values of Qn analytes ranged from 75±5.4% to 92±1.6% (Table 1). For
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Textile 1, average recovery values ranged from 74±2.0 to 93±1.8% (Table 1) and are comparable to the
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recovery values reported for other methods.4, 5, 24 The lower recovery values correspond to longer
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chained analytes, such as Me-FOSE. Precision for Qn analytes ranged from 1.6-5.4% on papers and 0.4-
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3.8% on textiles. Instrumental precision (intra- and inter-day variability) for all analytes ranged between
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0.9-25% (Table S3). Inflated instrumental precision values were observed for analytes present in Textile
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9 at levels close to the LOQ for the respective analytes (10-14:2 FTOH, N-MeFOSE).
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For paper, LOD values for paper fell between 30-77 ng/g, while textile LODs were roughly a factor of two
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lower, ranging from 19-34 ng/g (Table 1). Values for LOD and LOQ in units of µg/m2 are given in the SI in
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order to facilitate direct comparison with the literature. (Table S2). The LOQ for other methods are set 11 ACS Paragon Plus Environment
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as the lowest point of the calibration curve, typically corresponding to a value of 5-10 pg/µL.3, 24 By
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comparison, the presented method results in a factor of 5-10 lower LOQ values for all analytes, due to
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the 1 pg/µL calibration standard at the lowest end of our calibration curve.
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Kotthoff et al., reported whole method LOQ values for both papers and textiles, but for FTOHs only.5 The
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LOQ values reported were 1 ng/g and 0.3-0.8 µg/m2 for papers and textiles respectively. The area of
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material used in the study of Kotthoff et al. corresponds to 100 cm2 for papers and a range of 4-5 cm2 for
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textiles.5 The total area of paper and textiles used in the presented method (2.25 cm2) are a factor of 44
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and 2.25 times lower respectively. Thus, the method of Kotthoff et al. has an estimated factor of three
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times lower LOQ for papers and textiles compared to the presented method when material area is taken
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into account. The difference in LOQ between Kotthoff et al. and the presented method is due to the
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simplicity of the presented method. The lack of other processing steps offers great savings in time and
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minimizes loss of highly volatile analytes, such as the 4:2 FTOH. However, a drawback of the presented
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method is the reduction of sensitivity due to the lack of an extract concentration step. A factor of 2.5
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increase in sensitivity is obtained with a 50-µL injection. However, for a 50-µL injection volume, the
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upper calibration limit is lower. While there are more sensitive methods for the UPLC-MS/MS analysis of
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FTOHs that require derivatization and clean up steps,20, 39 eliminating derivatization and clean-up steps
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as described for this method offer greater time savings, while preserving the number of volatile PFASs
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analyzed.
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Non-Targeted Analysis
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Non-Targeted analysis by GC-QTOF revealed higher chained homologs of previously reported
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fluorotelomer alcohols such as the 12:2 and 14:2 FTOH.19, 20 The homologs 16:2 and 18:2 FTOH as
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reported by Yuan et al.,20 were not observed. The additional FTOH homologues observed were unique to
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samples (Textile 8 and 9) which dated before the year 2000, illustrating the difference in analyte
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distribution pre- and post- the C8 phase out. Additionally, two series of homologues from both the N-
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MeFASE and N-EtFASE families were revealed by non-targeted analysis (Figure 3). Using the confidence
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tiers reported in Schymanski et al., detected homologous series all fall within the confidence level 2b.40
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In the case of the N-MeFASE family, homologs containing three to seven carbons were observed in
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Textiles 8 and 9 in addition to the known C8 homolog (N-MeFOSE). In the case of the N-EtFASE family,
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homologs containing two to seven carbons were observed in addition to the known C8 homolog (N-
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EtFOSE). Through non-targeted analysis, 13 additional homologs of known classes (two FTOHs, five
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MeFASEs, and six EtFASEs) were identified, but no new classes were observed. The number of new
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analytes more than doubles the number of analytes currently incorporated in other methods for volatile
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PFAS analysis in consumer products.3-5, 24 Thus, the final analyte list used in the method demonstration
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of the presented paper incorporates a total of 21 individual analytes, as opposed to other methods that
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incorporate a maximum of eight volatile PFASs in the analysis of papers and textiles.
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Method Demonstration
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Papers. The papers selected for method demonstration were all unused materials. Only fluorotelomer-
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based FTOHs were quantified on papers purchased in 2017; no ECF-based PFASs were observed (Table
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2). Concentrations of FTOHs detected on paper samples ranged from
