Identification of Novel Hydrogen-Substituted Polyfluoroalkyl Ether

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Identification of novel hydrogen-substituted polyfluoroalkyl ether sulfonates in environmental matrices near metal-plating facilities Yongfeng Lin, Ting Ruan, Aifeng Liu, and Guibin Jiang Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b02961 • Publication Date (Web): 18 Sep 2017 Downloaded from http://pubs.acs.org on September 19, 2017

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Environmental Science & Technology

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Submit for publication in Environmental Science & Technology

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Identification of novel hydrogen-substituted polyfluoroalkyl ether

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sulfonates in environmental matrices near metal-plating facilities

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Yongfeng Lin1,2, Ting Ruan1,2*, Aifeng Liu1,3, Guibin Jiang1,2

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State Key Laboratory of Environmental Chemistry and Ecotoxicology,

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Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences,

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Beijing, 100085 2

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University of Chinese Academy of Sciences, Beijing 100049, China

CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101, China

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*Corresponding author

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Dr. Ting Ruan

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Research Center for Eco-Environmental Sciences,

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Chinese Academy of Sciences

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Tel: 8610-6284-9334

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Fax: 8610-6284-9179

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E-mail: [email protected]

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ACS Paragon Plus Environment


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Abstract

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Environmental occurrence and behaviors of 6:2 chlorinated polyfluoroalkyl ether

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sulfonate (Cl-6:2 PFESA, with trade name F-53B) have been receiving increased

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attention recently. Nevertheless, its potential fates under diversified conditions remain

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concealed. In this study, susceptibility of Cl-6:2 PFESA to reductive dehalogenation

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was tested in an anaerobic super-reduced cyanocobalamin assay. A rapid transformation

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of dosed Cl-6:2 PFESA was observed, with a hydrogen-substituted polyfluoroalkyl

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ether sulfonate (1H-6:2 PFESA) identified as the predominant product by a non-target

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screening workflow. With the aid of laboratory-purified standards, hydrogen-

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substituted PFESA analogues (i.e. 1H-6:2 and 1H-8:2 PFESA) were further found in

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river water and sediment samples collected from two separate regions near metal-

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plating facilities. Geometric mean concentrations of 560 pg/L (river water) and 11.1

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pg/g (sediment) for 1H-6:2 PFESA and 11.0 pg/L (river water) and 7.69 pg/g (sediment)

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for 1H-8:2 PFESA were measured, and both analytes consisted average compositions

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of 1% and 0.1% among the eighteen monitored per- and polyfluoroalkyl sulfonate and

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carboxylate pollutants, respectively. To our knowledge, this is the first to report

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existence of polyfluoroalkyl sulfonates with both hydrogen and ether functional group

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in the environment.

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1. Introduction

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Per- and polyfluoroalkyl substances (PFASs) are considered as a group of ubiquitous

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xenobiotic contaminants. In particular, perfluoroalkyl sulfonates (PFSAs) and

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perfluoroalkyl carboxylates (PFCAs) were detected in various environmental

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compartments and biological species.1-4 Their persistent, bioaccumulative and toxic

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behaviors have triggered restrictions on usages and voluntary phase-out initiatives.5,6

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Increasing attention has been paid on the identification of novel fluorinated chemicals,

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because analogues with diverse functional groups were found in the environment. For

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instance, a series of hydrogen- and chlorine-substituted PFCAs were discovered in

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wastewater from combined fluorochemical manufacturing origins.7 Perfluoroalkyl

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ether carboxylates and sulfonates were noticed in natural water downstream the

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locations where wastewater treatment plant and industrial effluent streams occurred.8,9

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6:2 Chlorinated polyfluoroalkyl ether sulfonate (Cl-6:2 PFESA, trade name: F-53B)

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is used as an alternative of perfluorooctane sulfonate (PFOS) products in metal plating

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industry.10 Much concern has been specially focused on this chemical recently, due to

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discoveries of its widespread presence in riverine water,11 sewage sludge,12 aquatic

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organism13,14 and human serum.15 Longer-chain analogues, i.e. Cl-8:2 and Cl-10:2

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PFESA, were also recognized, which were considered as impurity components released

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from the F-53B product usages.12 Based on up-to-date knowledge, the residue levels,

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persistent and bioaccumulative properties, and elimination kinetics in human exposure

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of Cl-6:2 PFESA were comparable with those of PFOS in the investigation 3



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scenarios.10,13,15 Nevertheless, environmental behaviors associated with the unique

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chlorine atom in the Cl-PFESA molecular structure were yet uninvestigated.

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A diversity of analytical techniques were applied for the identification of unknown

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fluorinated compounds, in which liquid chromatography coupled with high-resolution

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mass spectrometry (LC-HRMS) emerged as a powerful tool.7,16-18 With the aid of fast

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atom bombardment and quadrupole-time-of-flight HRMS instruments, accurate masses

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and elemental formulas of ions with suspected functional groups and carbon chain

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length were screened, which resulted in discovery of zwitterionic, cationic and anionic

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fluorotelomer sulfonates in commercial aqueous film-forming foam products.16 Mass

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defect filtering could be used as an effective protocol to exclude quantity of irrelevant

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information in MS spectrum. Polyfluorinated carboxylates and sulfonates were

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distinguished in manufacturing wastewater by visualizing existed series of homologues

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in horizontal lines in the CF2 adjusted Kendrick mass defect (AKMD) plot.7,17

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Meanwhile, a case-control strategy using LC-quadrupole time-of-flight tandem mass

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spectrometry and statistical analysis was developed to elucidate analytes with

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significantly different abundances, which led to recognition of chlorine- and ketone-

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substituted PFOS derivatives in sera of firefighters.18 A combination of these techniques

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is also requisite for illumination of PFAS precursor transformation processes in the

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environment.19

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Reductive dehalogenation is vital in microbial transformation of chlorinated and 4


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brominated pollutants in anaerobic environment.20 The in-vitro assay using corrinoid

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macro-cycles, i.e. cyanocobalamin, as catalysts is a simplified biomimetic system to

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imitate the anaerobic biotransformation behaviors. Super-reduced cyanocobalamin

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(CCA, Vitamin B12) was confirmed functional to decompose branched isomers of PFOS

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and technical product under certain incubation conditions.21 Similar assays were further

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applied for prediction and confirmation of potential microbial degradation metabolites.

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For instance, tri- and tetra-ortho substituted congeners generated from incubation of

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polybrominated biphenyls (PBBs) in super-reduced CCA assay could match the

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composition pattern of PBB residues in Baltic cod liver.22 Coincidence on major

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debromination pathways of decabromodiphenyl ether was observed by comparison of

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characteristic metabolites in the super-reduced CCA assay and in sediment.23

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In this study, a LC-HRMS non-target screening workflow was established with the

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aim (1) to test transformation feasibility of Cl-6:2 PFESA in anaerobic environment by

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using a super-reduced CCA assay; (2) to screen for major terminal transformation

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products; (3) to check the existence and behaviors of relevant chemicals in the

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environment.

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2. Materials and Methods

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2.1 Chemicals and reagents

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The Cl-6:2 PFESA and Cl-8:2 PFESA standards were laboratory-purified from

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commercial F-53B mist suppressant product, with purification methodology and 5



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structural characterization described elsewhere.12 A native PFSAs and PFCAs standard

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mixture (PFAC-MXB, 2 μg/mL for each analyte), native fluorotelomer sulfonates (4:2,

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6:2 and 8:2 FTSA, 50 μg/mL for each analyte), and isotope-labeled standards

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(MPFHxA, MPFOA, MPFUdA, MPFDoA, MPFHxS, MPFOS, M2-6:2 FTSA,

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M5PFHxA, M6PFDA, M3PFHxS, M8PFOS, 50 μg/mL for each standard) were

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obtained from Wellington Laboratories (Ontario, Canada). Cyanocobalamin, ENVI-

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Carb powder (120 – 400 mesh, 100 m2/g) and sodium citrate tribasic dehydrate were

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purchased from Sigma-Aldrich (St. Louis, MO). Ammonium hydroxide (NH4OH, 50%,

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v/v) and sodium carbonate were from Alfa Aesar. HPLC grade acetic acid and

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ammonium acetate were obtained from DikmaPure (LakeForest, CA). Sodium

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hydroxide, concentrated hydrochloric acid (37%) and titanium (III) chloride (TiCl3, 20%

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w/v solution in 2N hydrochloric acid) were acquired from Sinopharm Chemical

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Reagent, Inc. (Beijing, China), Merck (Darmstadt, Germany) and Acros Organics

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(Belgium, Germany) respectively. The purities of all chemicals were 95% or higher

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unless otherwise stated. HPLC-grade methanol was supplied by J.T. Baker

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(Phillipsburg, NJ). Ultrapure water (18.3 MΩ·cm) was generated by a Milli-Q system

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(Millipore, Billerica, MA).

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2.2 In-vitro reductive transformation assay

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Super-reduced CCA assay was prepared according to literature with minor

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modifications,24,25 and detailed procedures were given in the Supporting Information.

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Transformation process was performed by mixing 400 μL of 1.0 mg/mL Cl-6:2 PFESA 6


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(in methanol) and 1 mL of super-reduced CCA solution in 15 mL polypropylene

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centrifugation tubes at room temperature (25 ± 2 °C). Each sample was operated

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individually at designated time intervals, with a maximum incubation time of 240

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seconds. At each appointed incubation time, 3.6 mL of methanol was added to

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effectively dilute and retard transformation process (Figure S1). The samples were then

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transferred outside the anaerobic chamber, and purged with ambient air to finally

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quench reactions.24 Control samples containing the same amounts of dosed analytes,

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solvent and agents except for CCA (CCA-lacking assay) were also performed.

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Supernatants were obtained by centrifugation at 6600 g for 10 min, which were diluted

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both 2- and 2000-fold in methanol. One milliliter of each diluted supernatant was

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transferred to LC vials for instrumental analysis, with 20 ng of isotope-labeled standard

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mixture (M3PFHxS, MPFOS, M8PFOS and M2-6:2 FTSA, 2 μg/mL in methanol for

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each standard) added in order to monitor matrix effects.

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2.3 Sampling and pretreatment procedures

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A total of sixty river water and sediment samples were collected in two separate

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sampling regions (Fenghuajiang River in Zhejiang Province, and Pan River in

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Shandong Province) in May 2016, in order to verify whether potential transformation

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products found in the super-reduced CCA assay could be identified in real environment.

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Sampling sites were located upstream and downstream of electroplating factories. River

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water samples were collected ~ 0.4 m below the water surface using 1 liter

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polypropylene bottles, which were pre-cleaned by methanol and ultrapure water. 7



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Sediment samples with a depth of 3 – 5 cm were gathered using a grab sampler (Wildco

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Ekman Grab, Buffalo, NY), packed in aluminum foil and stored in polypropylene zip

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bags. All samples were preserved at zero Celsius placing on ice in the field and

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transported back to laboratory immediately. Water samples were kept at 4 °C, and

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sediment samples were freeze-dried, homogenized and stored at -20 °C until analysis.

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River water samples were pretreated by solid phase extraction (SPE) according to

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literature.26 In brief, 200 mL of water was filtered through a glass microfiber filter (0.7

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μm, Whatman Inc., Pittsburgh, PA), and the filter was washed by 5 mL of methanol to

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prevent possible analyte loss. The combined sample was spiked with 1 ng of each

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surrogate standard including MPFHxA, MPFOA, MPFUdA, MPFDoA, MPFHxS,

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MPFOS and M2-6:2 FTSA. It was then loaded onto a HLB cartridge (Waters Inc.,

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Milford, MA) at a flow rate of 5 – 6 mL/min, which was preconditioned by 4 mL of

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methanol and 4 mL of ultrapure water. The cartridge was then dried under vacuum and

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eluted by 3×2 mL methanol, and the eluent was concentrated to a final volume of 200

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μL by a gentle nitrogen flow. For sediment samples, an alkaline extraction method27

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was used with minor modifications. Approximately 1.0 g of sediment was included in

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a 15 mL polypropylene centrifugation tube, spiked with 1 ng of each surrogate standard,

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and soaked in 1 mL of 100 mM NaOH in methanol/H2O (v/v, 4:1) for 1 h. Three

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milliliters of methanol was then added into the tube, which was ultrasonic extracted

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(600 W at room temperature) for 30 min and shaken at 250 rotations per minute for

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another 1 h. Supernatant was collected after centrifugation at 1500 g for 10 min, and 8


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the extraction process was repeated. All supernatants were combined, concentrated to

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~ 2 mL, and diluted with 100 mL of ultrapure water. The same SPE procedure as

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described for the river water samples was then additionally applied to enrich potential

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fluorinated chemicals. All samples were spiked with 1 ng of each isotope-labeled

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injection standard (M5PFHxA, M6PFDA, M3PFHxS, and M8PFOS) before

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quantification analysis.

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2.4 Qualitative and quantitative analysis

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An ultrahigh performance liquid chromatograph-Orbitrap Fusion mass spectrometer

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system (Thermo Fisher Scientific Inc., Waltham, MA) was operated in negative

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electrospray ionization mode, which was applied for both qualitative and quantitative

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purposes. An ACQUITY C18 column (Waters, 1.7 µm, 2.1×100 mm) was used for

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analyte separation. Column temperature was 35 °C, and flow rate was set as 0.3 mL/min.

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The flow gradient initiated at a composition of 25:75 (methanol/water, v/v, 1mM

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NH4Ac additive in each phase), held for 1 min, linearly switched to 80% methanol in 5

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min, and finally reached 100% methanol in another 3 min. Full-scan mass spectrum

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(MS1, scan range of 150 – 1500 m/z) was obtained with a full width at half maximum

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(FWHM, at m/z = 200) resolution of 120000 for accurate mass measurement and

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retrospective quantification of identified PFAS chemicals.28 Information of both

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precursor ions and characteristic daughter ions was generated in high resolution MS

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fragmentation (MSn) mode for chemical structure elucidation. MS1 precursors selected

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by quadrupole with an isolation window of 1 m/z were transferred to the Ion Routing 9



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Multipole (IRM) for MS2 fragmentation at higher-energy collisional dissociation (HCD)

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energy of 20 – 60%. For MS3 fragmentation, the ions in IRM were transported to the

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ion trap, filtered at an isolation window of 2 m/z, and transferred back for fragmentation

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at HCD energy of 30% with an resolution of 60,000 (FWHM at m/z = 200). HRMS

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instrumental performance was checked every week by using Pierce ion calibration

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solution kit (Thermo Fisher Scientific Inc., Waltham, MA) to ensure accurate mass

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precision of reference materials in the range of 2 ppm.

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For identification of potential Cl-6:2 PFESA transformation products in reductive

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environment, a non-target screening workflow was established (Figure S3). Full-scan

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MS1 spectrum of 10 samples during the first 10 – 100s incubation time in super-reduced

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CCA assay were used as the dataset of metabolite-transformation group, and those of

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another 10 samples from the CCA-lacking assay at the same 10 – 100s incubation time

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were selected as the dataset of dosed-control group in order to maximum eliminate

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irrelevant information in the LC vials. All raw data was introduced in the XCMS

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processing package for peak detection, with further feature filtering and statistical

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ranking protocols performed mainly constituted of the 80% Rule,29 Kendrick mass

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defect, intensity threshold, and orthogonal partial least-squares-discriminant analysis.

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Chemical structure confirmation was based on deprotonated monoisotopic mass (MIM),

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retention time (RT), isotope distribution, and MSn fragmentation ion analysis. The

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identified PFAS compounds were additionally searched in the river water and sediment

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samples by a suspect screening procedure (Table S3). Occurrence of novel fluorinated 10


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contaminants was verified by comparison of MIM, RT and MSn with laboratory-

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purified standards. More detailed information on data analysis was summarized in the

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Supporting Information.

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2.5 Quality assurance and Quality control (QA/QC)

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For evaluation of instrumental performance in the super-reduced CCA assay, one

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blank injection (pure methanol) was included in each batch of two 2-fold diluted

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samples as well as in each batch of five 2000-fold diluted samples to monitor residue

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levels of Cl-6:2 PFESA and metabolites in LC-MS instrumental system. Few Cl-6:2

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PFESA was found, with no metabolites observed. No subtraction was thus made for

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analyte quantification because maximum Cl-6:2 PFESA residue was < 0.14% of the

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amount dosed in each sample. Quantified results of isotope-labeled injection standards

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based on external calibration curves were 98%, 97%, 94% and 97% for M3PFHxS,

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MPFOS, M8PFOS and M2-6:2 FTSA, suggesting negligible matrix effect in the super-

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reduced CCA assay. Quality control samples (QCs, n = 10) were acquired by mixing a

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certain amount (200 µL) of supernatant from each sample after transformation process,

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which were 2-fold diluted by methanol and injected in every batch of five injections.

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Significant correlations of instrumental responses (IRs, R = 0.914 – 0.964, p < 0.05)

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were observed for all the 3613 features co-existed in the QCs, suggesting sufficient

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performance of replication in the qualitative analysis procedure.

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For quantification of PFAS analytes in the environmental samples, two procedure 11



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blanks of 200 mL of ultrapure water or 1.0 g of methanolic pre-washed diatomaceous

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earth (Dionex, Sunnyvale, CA) were added in each batch of eight river water and

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sediment samples, respectively. Most of the target analytes were not detectable except

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for trace amounts (~ 0.15 pg on column) of Cl-6:2 PFESA, which contributed to < 5%

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of averaged concentrations in the same batch of samples. Instrumental drift in

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sensitivity was verified daily by continuous injection of 0.01 – 1.0 ng/mL (n = 7, R =

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0.989 – 0.999, p < 0.05) and 1.0 – 50 ng/mL (n = 6, R = 0.991 – 0.999, p < 0.05)

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methanolic standard solution. Method quantification limits (MQLs, Table S5)

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calculated by a signal/noise ratio of ten ranged from 14 pg/L (1H-8:2 PFESA) to 218

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pg/L (PFHxA) in river water and 9 pg/g (1H-8:2 PFESA) to 37 pg/g (PFOS) in sediment

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samples, respectively. Average recoveries of isotope-labeled surrogate standards (n =

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30, 1 ng for each standard, Table S7) were 71% (MPFHxA) to 108% (MPFOS) in river

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water and 70% (MPFUdA) to 86% (M2-6:2 FTSA) in sediment samples, individually,

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indicating internal calibration quantification was applicable for the target analytes.

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Minor ionization suppression was observed, as matrix interferences of the isotope-

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labeled injection standards (n = 30, spiked at 1 ng for each standard, Table S6) were in

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the range of 86% (M6PFDA) to 95% (M8PFOS) in river water and 84% (M6PFDA) to

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90% (M5PFHxA) in sediment samples. No blank contamination subtraction nor matrix

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effect correction was made for all measured analyte concentrations.

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2.6 Statistical analysis Feature identification including data deconvolution, peak detection, retention 12


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alignment, and scaling was performed by the XCMS software.30 All processed

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information (e.g. accurate mass, intensity, retention behavior of each feature) was then

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aligned together in an Excel file (Table S1). Orthogonal partial least-squares-

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discriminant analysis (OPLS-DA, SIMCA-P 13.0, Umetrics, Umeå, Sweden) was

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carried out to rank all features with respect to variations in transformation process.

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Xcalibur software (Thermo Scientific, USA) was used for both qualitative and

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quantitative analysis. Correlations of IRs among co-existed features in QC samples, and

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correlations in concentrations between quantified PFAS analogues in river water

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samples were assessed by Spearman's test using SPSS V17.0 for Windows Release

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(SPSS Inc. 2009). Significant level was set as p < 0.05 unless otherwise mentioned.

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Geometric mean, concentration range, detection frequency and average composition

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were used to describe the quantification results of target analytes in river water and

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sediment samples.

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3. Results and Discussion

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3.1 Changes of chemical profiles in the in-vitro assay

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Proper case-control sampling could be an effective data-mining strategy, which was

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applied to emphasize differences in chemical profiles between experimental and control

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samples in investigated conditions.18 A total of 3389 features were recognized in all raw

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data of both metabolite-transformation and dosed-control groups. Twenty-six features

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were finally discerned after filtering and ranking protocols, which illustrated Cl-6:2

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PFESA and potential metabolite candidates in elimination (DOWN) and generation (UP) 13



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trends with high constituent abundances, respectively.

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Among the features shown in Table S1, accurate MIM = 530.8949 was present with

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a mass error of Δm = -1.28 ppm compared with exact mass of Cl-6:2 PFESA ([M(35Cl)-

290

H]-, MIM = 530.8956). It could be easily recognized as the dosed compound into the

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in-vitro assay, as reproducible LC retention behaviors (RT = 7.85 min, Figure S7) were

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observed in sample supernatant and the Cl-6:2 PFESA standard. MS2 fragmentation

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pattern in HCD mode was further employed for analyte structure confirmation.

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Characteristic daughter ion [ClC6F12O]- (MIM = 350.9451, mass error: -0.15 ppm) in

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Figure S6-A clearly showed cleavage of ether bond, and formation of [FSO3]- (MIM =

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98.9555, mass error: -2.69 ppm) and [FSO2]- (MIM = 82.9606, mass error: -3.03 ppm)

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also verified existence of sulfonate functional group in the molecular structure. The 2.2

298

folds of average concentration in DOWN trend in metabolite-transformation group

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revealed Cl-6:2 PFESA elimination in the transformation process.

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The same identification protocol (Figure S3) was applied for screening of other

302

important features. The feature with the most abundant averaged IRs and isotopic peak

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clusters was noticed (MIM = 496.9338, RT = 7.19 min). Fragmentation pattern of this

304

feature was quite similar with that of Cl-6:2 PFESA (Figure S6-B). For instance,

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occurrence of [FSO3]- and [FSO2]- indicated the presence of sulfonate group in the

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molecular structure, and MIM = 198.9492 ([C2F5SO3]-,mass error: -0.90 ppm) and

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MIM = 316.9841 ([C6HF12O]-, mass error: -0.08 ppm) were a pair of daughter ions 14


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generated by ether bond cleavage. Interestingly, characteristic [C6F11O]- (MIM =

309

296.9779, mass error: 0.01 ppm) ion found both in this MS2 spectrum and in MS3

310

spectrum of [C6HF12O]- (Figure S9-A) suggested a neutral loss of HF in collision

311

process, which was further unzipped by dropping an additional CF2O carbon skeleton

312

to form [C5F9]- (MIM = 230.9861, mass error: -0.33 ppm). Thus, it could be identified

313

as one hydrogen-substituted metabolite (1H-6:2 PFESA). A minor mass error of Δm =

314

-1.51 ppm was observed between the measured MIM and exact mass of the

315

deprotonated [C8HF16SO4]- ion, and a 14.1-fold higher of averaged IRs in UP trend in

316

the metabolite-transformation group still showed its generation in the reductive assay.

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This chemical structure was further confirmed (Figure 1) by laboratory purified 1H-6:2

318

PFESA as described in the Supporting Information, which was supported by 1H and 19F

319

nuclear magnetic resonance spectrum. Therefore, a confidence level (CL) of Level 1

320

could be reached for both Cl-6:2 PFESA and 1H-6:2 PFESA according to structure

321

identification communicating criteria proposed by Schymanski et al.31

322 323

It is interesting to find that several deprotonated ions with molecular mass > 1000

324

Da were present in the recognized features (Table S1). The LC retention behaviors (RT

325

= 7.17 min) and MS2 fragmentation patterns (Figure S9-B and C) were almost the same

326

with that of 1H-6:2 PFESA. Formation of noncovalent homodimers has been reported

327

for a number of PFASs such as PFCAs, perfluorinated alkyl phosphates and

328

perfluoroalkyl ether carboxylates, due to facility of per- and polyfluorinated surfactants

329

to aggregate in gas phase in the MS source.9,32 Therefore, these deprotonated ions could 15



330

be assigned to isotopic clusters of [2M-2H+NH4]- and [2M-2H+Na]- (Table S2, M

331

representing 1H-6:2 and Cl-6:2 PFESA) adducts, with mass errors in the range of -0.39

332

– -1.39 ppm between measured MIMs and exact masses. [2M-H]- adducts also appeared

333

in the full-scan MS1 spectrum with significant contents, i.e. IRs > 107. These adducts

334

are indicators of parent ions but not irrelevant interferent formed by in-source collision

335

in MS instrument, as reaction probability of solvent (refer to NH4Ac additive in this

336

study) and metal adducts was discussed to be low.32

337 338

Other transformation products, including an unsaturated transit intermediate (1H-6:2

339

PFUESA, CL: Level 3) and a 2H-substituted metabolite (2H-6:2 PFESA, CL: Level

340

2b), and possible standard impurities (Cl-5:2 PFESA and 1H-5:2 PFESA, CL: Level 2b)

341

were also found in the reductive assay, with detailed information provided in Table S1.

342

Thus, a mass balance analysis of dosed Cl-6:2 PFESA and proposed transformation

343

products during the whole 10 – 240s incubation time was used to assess the reductive

344

transformation process. Except for Cl-6:2 and 1H-6:2 PFESA with laboratory purified

345

standards, instrumental responses of other proposed transformation products were

346

assumed equal to that of an equimolar amount of 1H-6:2 PFESA. A rapid

347

transformation of dosed Cl-6:2 PFESA in the super-reduced CCA assay was

348

surprisingly observed that the analyte was completely transformed within the exposed

349

period of 4 minutes (Figure 2). This transformation susceptibility of Cl-6:2 PFESA was

350

distinct from its persistent characteristic in the environment as generally

351

acknowledged.10,12,15 1H-6:2 PFESA (average yield in the equilibrium phase: 87.7 16


Page 16 of 37

Page 17 of 37


352

mol%) was the predominant analogue, followed by 1H-6:2 PFUESA (0.20 mol%) and

353

2H-6:2 PFESA (0.06 mol%). The total molar percentage recovery of all analytes was

354

in the range of 83.2 – 104 mol%, implying a majority part of PFAS chemicals in the

355

assay were investigated. The loss of additional amount of analyte might due to

356

adsorption onto labware33 or transformation into inorganic fluoride21 as reported for

357

other fluorinated compounds.

358 359

3.2 Occurrence and spatial distribution of 1H-PFESAs in the environment

360

The presence of Cl-PFESAs and other hydrogen-substituted PFESAs identified in

361

the super-reduced CCA assay was investigated by monitoring targeted accurate masses

362

in a suspect screening procedure (Table S3) in river water and sediment sample extracts

363

from two rivers, which are located in the regions with metal-plating activities. Cl-6:2

364

PFESA, Cl-8:2 PFESA (CL: Level 1) and the relevant 1H-substitiuted analogues (i.e.

365

1H-6:2 PFESA and 1H-8:2 PFESA, CL: Level 1) were identified in almost all of the

366

samples, suggesting their widespread distribution in the investigation areas. Exact

367

match of retention behaviors of the Cl-PFESA and 1H-PFESA compounds (RT = 7.21

368

– 8.71 min) were observed between both standard solutions and sample extracts (Figure

369

3-A). Characteristic neutral loss of C2F4SO3, HF and CF2O in MS2 spectrum of the

370

monitored ions in the collected samples were also comparable with those noticed in the

371

laboratory purified 1H-6:2 and 1H-8:2 standards (Figure 3-B and S6), illustrating the

372

sulfonate, hydrogen-substitution and ether function group in the molecular structures.

373

Meanwhile, no other relevant analogues were found in all samples, including Cl-5:2 17



374

and Cl-7:2 PFESA, 1H-5:2 and 1H-7:2 PFESA, 2H-6:2 PFESA and 1H-6:2 PFUESA.

375 376

Figure 4 showed spatial distribution of Cl-6:2 and 1H-6:2 PFESA from Fenghuajiang

377

River, Zhejiang Province. 1H-6:2 PFESA was found in most of the river water samples

378

(detection frequency: 88%) with concentrations in a range of N.D. – 3.31×103 pg/L

379

(geometric mean, GM: 799 pg/L). A decreasing trend of spatial concentrations for 1H-

380

6:2 PFESA was observed, which was quite similar with that of Cl-6:2 PFESA.

381

Significant correlation in concentrations between Cl-6:2 PFESA and 1H-6:2 PFESA

382

(Table S8, R = 0.914, p < 0.01) was also found, which might indicate potential impact

383

of metal plating activities in this area. Low residue levels of 1H-6:2 PFESA and 1H-

384

8:2 PFESA were also quantified in sediment samples with concentrations in the range

385

of N.D. – 503 pg/g dry weight (d.w.; detection frequency: 18%) and N.D. – 165 pg/g

386

d.w. (detection frequency: 6%), respectively. Apart from the 1H-PFESAs, residue

387

levels of Cl-6:2 and Cl-8:2 PFESAs, 4:2, 6:2 and 8:2 FTSAs, C6 – C12 PFCAs and C4

388

– C10 PFSAs were monitored as well. Perfluorooctanoate (PFOA) was the most

389

predominant PFAS contaminant (GM: 6.36×104 pg/L), which constituted 40 – 52%

390

(mean: 46%, n = 17) of the total quantified PFAS concentrations (∑PFASs). It followed

391

by perfluorohexanesulfonate (PFHxS) and Cl-6:2 PFESA (GM: 3.05×104 pg/L and

392

1.93×104 pg/L, respectively) with mean proportions of 24% and 14% in ∑PFASs,

393

respectively. Our results were in accordance with previous study by Lu et al.34 that

394

PFOA was also the most significant PFAS pollutant in Fenghuajiang River with a

395

concentration of 53 ng/L. Among all the identified PFAS compounds, 1H-6:2 PFESA 18


Page 18 of 37

Page 19 of 37

396


accounted for 0 – 1% (mean: 0.8%, n = 17) in the total quantified PFAS concentrations.

397 398

Different composition profiles of PFAS analogues were observed in sediment

399

samples, where 1H-6:2 PFESA and 1H-8:2 PFESA constituted 0 – 8% (mean: 1%, n =

400

17) and 0 – 4% (mean: 0.3%, n = 17) in ∑PFASs, respectively. The most abundant

401

PFAS pollutant was Cl-6:2 PFESA (GM: 1.77×103 pg/g d.w.), which comprised

402

proportions ranged from 8% to 77% (mean: 52%, n = 17) in ∑PFASs. The other

403

dominant PFAS analogues were Cl-8:2 PFESA (GM: 379 pg/g d.w.) and PFOA (GM:

404

177 pg/g d.w.), with a mean proportion of 16% and 13% in ∑PFASs, separately.

405 406

Significant abundances of the hydrogen-substituted analogues were also found in Pan

407

River in Shandong Province (Figure S2). 1H-6:2 PFESA was one of the abundant

408

fluoroalkyl substances in river water, with concentrations in the range of 97.3 pg/L –

409

1.25×103 pg/L (GM: 352 pg/L). Other analogues with comparable residue levels

410

included PFOA (GM: 5.87×103 pg/L), PFOS (GM: 3.85×103 pg/L), PFHxS (GM:

411

1.52×103 pg/L), Cl-6:2 PFESA (GM: 1.64×103 pg/L), 6:2 FTSA (GM: 807 pg/L) and

412

Cl-8:2 PFESA (GM: 33.3 pg/L). Similar composition was acquired in sediment samples

413

that the geometric mean concentration of 1H-6:2 PFESA was 10.0 pg/g, compared with

414

those of PFOS (GM: 254 pg/g), Cl-6:2 PFESA (GM: 149 pg/g), PFOA (GM: 55.3 pg/g),

415

and Cl-8:2 PFESA (GM: 37.2 pg/g), individually. The proportion of 1H-6:2 PFESA

416

were 0 – 7% (mean: 2%, n = 26) of total quantified C4 – C10 fluoroalkyl sulfonates and

417

carboxylates in the river water and sediment samples, and that of 1H-8:2 PFESA were 19



418

0 – 2% (mean: 0.3%, n = 26), separately.

419 420

Origins of the hydrogen-substituted analogues could partly be elucidated by

421

comparison of 1H-6:2 PFESA and Cl-6:2 PFESA residue levels in the commercial F-

422

53B mist suppressant product and in the investigated environmental compartments.

423

Existence of all possible PFESA analogues (Table S3) was firstly screened in the F-53B

424

product. Besides Cl-6:2 PFESA, Cl-8:2 PFESA (mass ratio relative to Cl-6:2 PFESA:

425

12%), Cl-10:2 PFESA (< 0.05%), Cl-7:2 PFESA (< 0.05%), Cl-5:2 PFESA (< 0.05%),

426

1H-6:2 PFESA (1%) and 1H-8:2 PFESA (0.4%) were found, but none of 2H-PFESA

427

nor 1H-PFUESA compound was detectable. Different mass ratios of 1H-6:2 PFESA to

428

Cl-6:2 PFESA were measured in river water and sediment samples from Fenghuajiang

429

River, which were in a range of 4 – 11% (mean: 6%, n = 15) and 3 – 23% (mean: 14%,

430

n = 3), respectively. Similar abundances were also observed in Pan River that the mass

431

ratios were in a range of 9 – 111% (mean: 27%, n = 13) and 2 – 18% (mean: 6%, n = 6)

432

in river water and sediment samples, separately, which were relatively higher than that

433

in F-53B commercial product (mean: 1%). It implied additional influencing factors

434

such as reductive dechlorination process and/or transport behaviors might be

435

responsible for 1H-6:2 PFESA contamination in the environment, besides pollution

436

caused by plausible emission from industry usage.

437 438 439

4. Environmental Implication This manuscript described the identification of major transformation products (i.e. 20


Page 20 of 37

Page 21 of 37


440

1H-6:2 PFESA, 2H-6:2 PFESA and 1H-6:2 PFUESA) of Cl-6:2 PFESA in the super-

441

reduced CCA assay. Hydrogen-substituted PFESA analogue (i.e. 1H-6:2 PFFESA and

442

1H-8:2 PFESA) were further observed in water and sediment samples for the first time.

443

The results indicated that dechlorination of Cl-PFESAs might be an indirect source of

444

H-PFESAs. Moreover, the established non-target screening workflow would provide

445

an effective tool for recognition of emerging fluorinated transformation products in the

446

environment.

447 448

Chlorine- and hydrogen-substituted polyfluoroalkyl substances were continuously

449

discovered in water,7,35 fish,36,37 and human sera18 recently, which have distinct

450

molecular functional groups compared with legacy PFCAs or PFSAs. The hydrogen

451

might have an influence on the behaviors of 1H-PFESAs in the environment. For

452

instance, the substitute of hydrogen makes the molecule more hydrophilic than Cl-

453

PFESAs and PFSAs with the same carbon-chain length, because weaker retention on

454

reversed-phase C18 HPLC column was observed (Figure S15, RT = 7.87 and 7.20 for

455

Cl-6:2 PFESA and 1H-6:2 PFESA, respectively). Less hydrophobic PFASs were

456

generally easier to transport in aquatic environment.38 The presence of hydrogen in the

457

fluorinated carbon backbone may provide potential sites for microbial degradation.

458

Fluorine removal with the aid of hydrogen attached to the adjacent carbon is a vital step

459

for telomerized fluorochemicals, especially fluorotelomer alcohols and X:3

460

fluorotelomer carboxylates.33,39 While, defluorination process for perfluoroalkyl

461

sulfonates are difficult, which often requires extreme physical-chemical conditions.21 21



462

Biodegradability and atmospheric degradation of ether-containing functional groups in

463

perfluoropolyethers (such as ADONA and GenX) were not found based on currently

464

incomplete information.40,41

465 466

A quick transformation of Cl-6:2 PFESA described in this manuscript was observed

467

in an anoxic reductive environment, which might not be contradictory to its persistence

468

reported in literature.10,13,15 The slow transformation of Cl-6:2 PFESA in the aerobic

469

closed bottle test did not meet readily degradability criteria according to OECD 301D,

470

and only minor loses (< 10%) under various abiotic oxidation conditions might suggest

471

its stability in photo-degradation and Fenton reactions in the environment.10 Estimated

472

human total elimination half-lives in the range of 10.1 – 56.4 years in fishery

473

employees15 and a median Log BAF(whole body) factor value of 4.322 found in crucian

474

carp13 further indicated strong biopersistence and bioaccumulation propensity of this

475

eight-carbon polyfluoroether sulfonate. Thus, more detailed investigation is warranted

476

to reveal impacts of chlorine and hydrogen atoms on the fate of novel polyfluorinated

477

substances in diverse environmental-relevant conditions.

478 479

Acknowledgements

480

We thank the National Natural Science Foundation (21622705, 21361140359,

481

21577151, and 21621064) and the Youth Innovation Promotion Association CAS

482

projects for joint financial support.

483 22


Page 22 of 37

Page 23 of 37


484

Supporting Information

485

Preparation of CCA assay; non-target screening workflow; laboratory purification of

486

1H-6:2 and 1H-8:2 PFESA standards; and spike recovery experiments in water and

487

sediment samples; (Table S1) features with VIP > 1 generated in the non-target

488

screening workflow; (Table S2) homodimers of Cl-6:2 and 1H-6:2 PFESA; (Table S3)

489

detailed information of PFASs in suspect screening procedure; (Table S4) instrumental

490

parameters on chromatographic separation and mass spectrometry; (Table S5) MQLs

491

of PFAS analytes in water and sediment samples; (Table S6 and S7) recoveries of PFAS

492

analytes and surrogate standards in water and sediment samples; (Table S8 and S9)

493

descriptive statistics and correlation analysis of quantified PFAS concentrations;

494

(Figure S1) methanol dilution effectively retarded transformation; (Figure S2) sampling

495

map in Pan River; (Figure S3) non-target screening workflow; (Figure S4 and S5) PCA

496

and OPLS-DA analysis; (Figure S6-S9) total ion chromatography and MSn spectrum of

497

Cl-6:2 PFESA, transformation products and homodimers; (Figure S10) tentative

498

molecular structures of 2H-PFESA and 1H-6:2 PFUESA; (Figure S11-S13) LC

499

separation and structure characterization of 1H-6:2 and 1H-8:2 PFESA laboratory-

500

purified standards; (Figure S14) extraction efficiency in sediment samples; (Figure S15)

501

retention behaviors of linear-PFOS, Cl-6:2 and 1H-6:2 PFESA on reversed C18 column.

502

The material is available free of charge via the Internet at http://pubs.asc.org.

503 504

23



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39. Wang, N.; Buck, R.C.; Szostek, B.; Sulecki, L.M.; Wolstenholme, B.W. 5:3

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Polyfluorinated acid aerobic biotransformation in activated sludge via novel “one-

651

carbon removal pathways”. Chemosphere 2012, 87 (5), 527-534; DOI

652

10.1016/j.chemosphere.2011.12.056.

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40. Young, C.J.; Hurley, M.D.; Wallington, T.J.; Mabury, S.A. Atmosphere lifetime and

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global warming potential of a perfluoropolyether. Environ. Sci. Technol. 2008, 40

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(7), 2242-2246; DOI 10.1021/es052077z.

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41. Wang, Z.Y.; Cousins, I.T.; Scheringe,r M.; Hungerbühler, K. Fluorinated

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alternatives to long-chain perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkane

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sulfonic acids (PFSAs) and their potential precursors. Environ. Int. 2013, 60, 24230


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248; DOI 10.1016/j.envint.2013.08.021.

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Figure Legends:

661 662

Figure 1. Chemical names, acronyms and confirmed molecular structures (CL: Level

663

1) of Cl-PFESAs and 1H-PFESAs.

664 665

Figure 2. Total mass balance and transformation dynamics of Cl-6:2 PFESA, 1H-6:2

666

PFESA, 2H-6:2 PFESA and 1H-6:2 PFUESA in the CCA assay at incubation time of

667

10 – 240s (n = 20).

668 669

Figure 3. Chromatographic behaviors and MS2 fragmentation patterns of identified Cl-

670

PFESAs and 1H-PFESAs in river water and sediment samples. (A. retention time of

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Cl-PFESAs and 1H-PFESAs in standard solution and sample extracts; B. proposed MS2

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fragmentation patterns of identified Cl-PFESAs and 1H-PFESAs in sample extracts.)

673 674

Figure 4. The sampling map showing spatial distribution of Cl-6:2 PFESA and 1H-6:2

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PFESA in river water samples from Fenghuajiang River in Zhejiang Province. (Pink

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polygon, electroplating industrial park; black tetragon, sampling sites for river water

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and sediment samples. The latitudes of the investigated region ranged from 29° 47' 0"

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N to 29° 59' 0" N and longitudes from 121° 29' 0" E to 121° 45' 0" E).

679 680

TOC ART (image created by the authors in the original manuscript submission)

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Figure 1. 145x65mm (300 x 300 DPI)



Figure 2. 138x121mm (300 x 300 DPI)


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Figure 3 241x170mm (300 x 300 DPI)



Figure 4. 247x146mm (300 x 300 DPI)


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TOC ART 84x45mm (300 x 300 DPI)


Identification of Novel Hydrogen-Substituted Polyfluoroalkyl Ether

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