The Chemours Company
Fayetteville Works
22828 NC Highway 87 W
Fayetteville, NC 28306

PFAS NON-TARGETED ANALYSIS AND
METHODS INTERIM REPORT #5
Process and Non-Process Wastewater and StormwaterPrepared by

The Chemours Company FC, LLC
Fayetteville Works
22828 NC Highway 87 W
Fayetteville, NC 28306

June 30, 2022

The Chemours Company
Fayetteville Works
22828 NC Highway 87 W
Fayetteville, NC 28306

TABLE OF CONTENTS
1INTRODUCTION ...............................................................................................................12

INVESTIGATION OF THE SECOND SET OF FIVE MOST ABUNDANTUNKNOWN PFAS IN GENERAL FACILITY DISCHARGE SAMPLES .......................43INVESTIGATION OF THE FIVE MOST ABUNDANT UNKNOWN PFAS IN
CHEMOURS PROCESS WASTEWATER SAMPLES .....................................................54SUMMARY AND NEXT STEPS .......................................................................................55REFERENCES ....................................................................................................................6ii

30 June 2022

The Chemours Company
Fayetteville Works
22828 NC Highway 87 W
Fayetteville, NC 28306

LIST OF TABLES
Table 1:

Status of Unknown PFAS - Interim Report #5

LIST OF FIGURES
Figure 1:

Extracted Ion Chromatograms (m/z 508.9357) of C8HF15O8 in Stormwater Sample
from Location 42 Collected March 17, 2022

Figure 2:

Tandem Mass Spectrometry Fragmentation Pattern of C8HF15O8

ACRONYMS AND ABBREVIATIONSCFRWCape Fear River Watch

Chemours

The Chemours Company FC, LLC

EIC

extracted ion chromatogram

Facility

Chemours Fayetteville Works, North Carolina

LCliquid chromatography

m/z

mass-to-charge ratio

MS/MStandem mass spectrometry

NCDEQ

NC Department of Environmental Quality

PFAS

per- and polyfluoroalkyl substances

QToF

quadrupole time-of-flight

TFA

trifluoroacetateiii

30 June 2022

The Chemours Company
Fayetteville Works
22828 NC Highway 87 W
Fayetteville, NC 28306

1

INTRODUCTION

This interim report has been prepared by The Chemours Company FC, LLC (Chemours) to provide
an update on the characterization of previously unidentified per- and polyfluoroalkyl substances(PFAS) in aqueous samples collected from process wastewater, non-process wastewater (i.e., noncontact cooling water) and stormwater at the Chemours Fayetteville Works, North Carolina site(the Facility). This work is being conducted pursuant to Paragraph 11 subpart (a) in the Consent
Order executed 25 February 2019 between Chemours and the North Carolina Department ofEnvironmental Quality (NCDEQ) with the Cape Fear River Watch (CFRW) as intervenor. The
overall purpose of this program is to identify previously unknown PFAS that may be present insamples of collected water and to develop standards and methods to facilitate the quantitative
analysis of these PFAS, as described in the PFAS Non-Targeted Analysis and Methods
Development Plan, Version 2 (Chemours and Geosyntec, 2019). This is the fifth interim report.
First Interim Report
The samples assessed via the non-targeted program were divided into two categories:••

General Facility Discharge samples - samples of stormwater, treated non-Chemours
process wastewater and/or non-contact cooling water discharging to the Cape Fear River.
These samples were collected at five locations; andChemours Process Wastewater samples - samples of process wastewater from Chemours
manufacturing areas. These samples were collected at two locations.

Samples were analyzed by liquid chromatography (LC) coupled to high-resolution quadrupole
time-of-flight (QToF) mass spectrometry (Chemours, 2020a). Unknown PFAS were assigned atentative empirical formula (defined as the number of atoms present in a compound but not thearrangement of the atoms) from unidentified chromatographic peaks with a signal-to-noise level
greater than six and using the atomic mass defect of fluorine as the molecular feature. An atomic
mass defect refers to the phenomenon that the mass of an atom is not exactly equal to the numberof subatomic particles (protons and neutrons) or the atomic mass number (except for carbon-12 bydefinition) as a result of differences in mass lost (as energy) when the atomic nucleus is formed
for each isotope. Fluorine is well-known to have a negative mass defect, where the exact mass isslightly less than the mass number. When the QToF mass spectrometer is operated in the negativemode, one can select fluorine-containing features and empirical formulas using available software
provided by the instrument vendor.
The tentative empirical formulas of the five most abundant unknown PFAS in each sample
category were:•General Facility Discharge - C4H5F3O2, C4H2F4O2, C6H6F6O2, C8H7F9O2 and C10H8F12O2;
and130 June 2022

The Chemours Company
Fayetteville Works
22828 NC Highway 87 W
Fayetteville, NC 28306•Chemours Process Wastewater - C8H2F14O7S, C8HF13O4, C8H5F13O6S, C9H2F14O6 andC6HF11O4.

None of the identified five potential PFAS in the General Facility Discharge samples wererepresented in the five potential PFAS in the Chemours Process Wastewater samples. These ten(10) unknown PFAS were advanced to the next step in the program - identifying molecularstructures (defined as the arrangement of the atoms into a molecule).
Second Interim Report
Investigation into the five most abundant unknown PFAS in the General Facility Discharge
samples revealed that four (C4H5F3O2, C6H6F6O2, C8H7F9O2 and C10H8F12O2) coeluted from theLC (Chemours, 2020b). These compounds have different molecular weights and were therefore
expected to be chromatographically resolved. Examination of the empirical formulas showed thatthe four compounds are related by C2HF3, that is, the addition of C2HF3 (trifluoroethylene, which
is a potential impurity in tetrafluoroethylene, a feedstock at the Facility) to each compound
generates the empirical formula of the following compound. This suggested that these fourcompounds may represent a single compound, C4H5F3O2, which, upon elution from the LC,
undergoes adduction 1 of C2HF3 in the ion source of the mass spectrometer. Furthermore, the single
compound C4H5F3O2 itself could be generated from a reaction between C2HF3 and acetate(CH3COO-, present in the LC eluent) in the ion source of the mass spectrometer. The fifth unknown
PFAS, C4H2F4O2, was not present in the samples at high enough concentrations to analyze by theQToF mass spectrometer.
Investigation into the five most abundant unknown PFAS in the Chemours Process Wastewater
samples concluded:•••••

C8H2F14O7S - the molecular structure was determined to be CF3-CF(COOH)-O-CF2CF(CF3)-O-CF2-CF2-SO3H;
C8HF13O4 - a molecular structure was tentatively identified for this unknown PFAS,
however, background interference in the samples had to date interfered with confirmationof the tentatively identified structure;
C8H5F13O6S - the molecular structure was determined to be HO3S-CF2-CF2-O-CF(CF3)CF2-O-CHF-CF2-OCH3;
C9H2F14O6 - the molecular structure was tentatively determined to be HOOC-CF2-CF2-OCF(CF3)-CF2-O-CF(CF3)-COOH; andC6HF11O4 - a molecular structure was not yet identified; background contamination in thesamples had to date interfered with confirmation of a tentatively identified molecularstructure.

Adduction is the process of the direct addition of two or more distinct molecules that result in a single reaction
product referred to as an adduct which containing all atoms of the two initial reaction molecules.

1230 June 2022

The Chemours Company
Fayetteville Works
22828 NC Highway 87 W
Fayetteville, NC 28306

Third Interim Report
The five most abundant unknown “PFAS” in the General Facility Discharge samples wereidentified to be sodium or potassium adducts of acetate clusters, containing no fluorine, rather than
PFAS (Chemours, 2021a). They were therefore eliminated from the list of unknown PFAS.
The third interim report (Chemours, 2021a) showed that (for the three remaining unidentified
PFAS of the five most abundant unknown PFAS in the Chemours Process Wastewater samples):•••C8HF13O4 was identified as EVE Acid, and was therefore no longer unknown;
C8H5F13O6S’s identified molecular structure was found to not match an existing authentic
standard, and therefore another molecular structure needs to be proposed; andC6HF11O4 was tentatively identified as CF3-O-CF2-O-CF2-CF2-CF2-COOH.

Fourth Interim Report
Because the first set of five most abundant unknown “PFAS” in the General Facility Discharge
samples turned out to be non-PFAS, the second set of five most abundant unknown PFAS in theGeneral Facility Discharge samples were carried forward to identification of their molecularstructures (Chemours, 2021b). In order of relative abundance, this resulted in the following:
••
•
•
•

C8HF15O8 was no longer detected in the original samples and, therefore, could not befurther investigated. A new sample from the same location (Location 42) was proposed forcollection during a rain event to investigate the presence and temporal stability of thiscompound;
C4H2F6O2 was identified as the sodium salt of a trifluoroacetate (TFA) and acetate adduct.
The correct formula was identified as C4H4F3O4Na;
C8HF13O4 was identified as R-EVE;
C4HF9O2S was identified as the sodium salt of sulfuric acid and acetate dimer adduct. The
correct formula was identified as C4H7SO8Na3. This compound is not a PFAS; andC6H3F7O2 was identified as the sodium and potassium salt of an acetate dimer. The correct
formula was identified as C6H10O6NaK. This compound is not a PFAS.

There was one remaining unidentified PFAS (of the five most abundant unknown PFAS) in theChemours Process Wastewater samples (C8H5F13O6S) for which the molecular structure identified
was found to not match an existing authentic standard in Interim Report 3; a tentatively identified
molecular structure for this unidentified PFAS continued to be in development.
Fifth Interim Report
This fifth interim report provides an update on:•

the identification of C8HF15O8 (the one remaining unknown PFAS in the top 10
unidentified PFAS in the General Facility Discharge samples); and330 June 2022

The Chemours Company
Fayetteville Works
22828 NC Highway 87 W
Fayetteville, NC 28306•efforts to further identify the molecular structures of the four most abundant unknown
PFAS in the Chemours Process Wastewater samples.

The remainder of this report consists of:•••2

Section 2: Investigation of the Second Set of Five Most Abundant Unknown PFAS inGeneral Facility Discharge Samples
Section 3: Investigation of the Five Most Abundant Unknown PFAS in Chemours Process
Wastewater Samples; andSection 4: Summary and Next Steps.

INVESTIGATION OF THE SECOND SET OF FIVE MOST ABUNDANTUNKNOWN PFAS IN GENERAL FACILITY DISCHARGE SAMPLESOf the second set of five most abundant unknown PFAS in the General Facility Discharge samples,
there was one remaining unidentified PFAS (C8HF15O8; mass-to-charge ratio 508.9357). ThisPFAS was observed in the General Facility Discharge sample from Location 42 (the location atwhich stormwater from rooftop gutters from the Chemours Monomers IXM area going to theCooling Water Channel is collected) when the sample was analyzed in March 2020. However, as
described in Interim Report #4, when the sample was re-analyzed in December 2021, the unknown
PFAS was not detected (Chemours, 2021b).
A new sample was collected from Location 42 on March 17, 2022 during a rain event and analyzed.
Initial analysis of the sample again showed that the peak (with a retention time of approximately
12.3 minutes) was not present. The sample was then concentrated 100-fold using solid-phaseextraction (SPE) and re-analyzed. The peak corresponding to the unknown PFAS was thenobserved.
Further analysis of the sample by tandem mass spectrometry (MS/MS) (Figure 2) resulted in theproposal of the following molecular structure for C8HF15O8:•

CF3-O-CF2-O-CF2-O-CF2-O-CF2-O-CF2-O-CF2-COOH

The current status of the second set of five most abundant PFAS in the General Facility Discharge
samples (as well as of the first set of five most abundant PFAS) is summarized in Table 1.

430 June 2022

The Chemours Company
Fayetteville Works
22828 NC Highway 87 W
Fayetteville, NC 28306

3INVESTIGATION OF THE FIVE MOST ABUNDANT UNKNOWN PFAS IN
CHEMOURS PROCESS WASTEWATER SAMPLES

Efforts to further identify the molecular structures of the four most abundant unknown PFAS inthe Chemours Process Wastewater samples is summarized below:••

three unknown PFAS (C8H2F14O7S, C9H2F14O6 and C6HF11O4) had tentatively identified
molecular structures identified in previous Interim Reports. Synthesis of authentic
standards for these compounds is the next step. Synthetic pathways are still being
developed; andone unknown PFAS (C8H5F13O6S) had a previously tentatively identified molecularstructure, which was found to be incorrect upon comparison to an existing authenticstandard. A revised tentatively identified molecular structure is still being developed.

The current status of the five most abundant PFAS in the Chemours Process Wastewater samples
is summarized in Table 1.

4

SUMMARY AND NEXT STEPS

A summary of results to date and the next steps for the potential unknown PFAS in General Facility
Discharge and Chemours Process Wastewater samples is provided below and in Table 1.
In the General Facility Discharge samples, the 10 most abundant unknown “PFAS” have been
identified:••••seven were identified as sodium or potassium adducts of acetate clusters. These are formedin the mass spectrometer source from sodium or potassium present in the sample matrix
and acetate or sulfate present in the LC eluent buffer. The incorrect empirical formulas(containing fluorine) were generated by the computer algorithm used to determine
empirical formulas and were mistakenly flagged as fluorinated compounds (Chemours,2021a). These compounds are not PFAS and the proposed empirical formulas have beenrevised showing the absence of fluorine;
one was identified as the sodium salt of a TFA acetate adduct. TFA is a known PFAS
associated with the Facility;
one was identified as R-EVE, which is a known PFAS associated with the Facility;
one was identified as an unknown PFAS, and a molecular structure has been proposed.

In the Chemours Process Wastewater samples, the five most abundant unknown PFAS have beenidentified:• one was identified as EVE Acid, which is a known PFAS associated with the Facility;• three were identified as unknown PFAS, and molecular structures have been proposed;
530 June 2022

The Chemours Company
Fayetteville Works
22828 NC Highway 87 W
Fayetteville, NC 28306•

one was identified as an unknown PFAS, and a molecular structure has not yet been
proposed.

Each sample category (General Facility Discharge and Chemours Process Wastewater) has at least
one unknown compound that has been determined to be a PFAS and for which a molecularstructure has been proposed. The next step will be to develop pathways for the synthesis of theauthentic standards for the proposed molecular structures on paper for the most abundant unknownPFAS in each sample category (C8HF15O8 for the General Facility Discharge samples andC8H2F14O7S for the Chemours Process Wastewater samples).
Once that has been completed, the compounds will be synthesized. Note that the synthetic
pathways are expected to be challenging, and this process may take considerable time to complete
given the complex structure of these compounds. Comparison of the liquid chromatography
retention time and tandem mass spectrometry fragmentation patterns of the authentic standard andthe unknown PFAS will aid in identification of the unknown PFAS.

5REFERENCES

Chemours, 2021a. PFAS Non-Targeted Analysis and Methods Interim Report #3. July 30, 2021.
Chemours, 2021b. PFAS Non-Targeted Analysis and Methods Interim Report #4. December 22,
2021.
Chemours, 2020a. PFAS Non-Targeted Analysis and Methods Interim Report. June 30, 2020.
Chemours, 2020b. PFAS Non-Targeted Analysis and Methods Interim Report #2. December 31,
2020.
Chemours and Geosyntec Consultants, 2019. PFAS Non-Targeted Analysis and Methods
Development Plan. Version 2. December 5, 2019.

630 June 2022

TABLE 1
STATUS OF UNKNOWN PFAS - INTERIM REPORT #5
Chemours Fayetteville Works, North Carolina
SampleSourceGeneral Facility
Discharge

Chemours
Process
Wastewater

Empirical Formula

Mass(Da)

Mass toCharge Ratio(m/z)

Tentative

Revised142.0241141.0168

C4H5F3O2*

C4H7O4Na

157.9983

156.9910

C4H2F4O2*

C4H6O4K

224.0272

223.0199

C6H6F6O2*

C6H10O6Na2Structures identified as sodium or potassium adducts of acetate
clusters; these are formed in the MS source from sodium orpotassium present in the sample matrix and acetate from the LC
eluent buffer.

306.0302

305.0230

C8H7F9O2*

C8H13O8Na3Compounds are not PFAS.

388.0331

387.0258

C10H8F12O2*

C10H16O10Na4

509.9432

508.9357

C8HF15O8--

CF3-O-CF2-O-CF2-O-CF2-O-CF2-O-CF2-O-CF2-COOH

Synthesis of an authentic standard is under consideration.

195.9956

194.9884

C4H2F6O2*

C4H4F3O4Na

Structure identified as sodium salt of TFA and acetate adduct.
Correct formula is C4H4F3O4Na

None

407.9670

406.9596

C8HF13O4--

Identified as R-EVE

None

283.9544

282.9471

C4HF9O2S*

C4H7SO8Na3240.0010

238.9937

C6H3F7O2*C6H10O6NaK

507.9302

506.9229

C8H2F14O7S--

CF3-CF(COOH)-O-CF2-CF(CF3)-O-CF2-CF2-SO3H

Synthesis of an authentic standard is under consideration.

407.9670

406.9598

C8HF13O4--

Identified as EVE AcidNone

475.9587

474.9515

C8H5F13O6S--

No proposed molecular structure yet

Continue to develop a proposed molecular structure.

471.9630

470.9556

C9H2F14O6--

HOOC-CF2-CF2-O-CF(CF3)-CF2-O-CF(CF3)-COOH

Synthesis of an authentic standard is under consideration.

345.9693

344.9620

C6HF11O4--CF3-O-CF2-O-CF2-CF2-CF2-COOH

Synthesis of an authentic standard is under consideration.

Proposed Molecular Structure

Structure identified as sodium salt of sulfuric acid and acetate
dimer adduct. Correct formula is C4H7SO8Na3. This compound
is not a PFAS.
Structure identified as sodium and potassium salt of acetate
dimer. Correct formula is C6H10O6NaK. This compound is not aPFAS.

Next Steps

None

None

None

Notes:* - tentative empirical formula has been revised following further investigation-- - revised empirical formula not requiredadduct - a product of a direct addition of two or more distinct molecules resulting in a single reaction product containing all atoms of all components- further investigation not required
C - carbon
LC - liquid chromatograph
Da - dalton
MS - mass spectrometerF - fluorine
O - oxygen
H - hydrogen
PFAS - per- and polyfluoroalkyl substances
S - sulfur

June 2022

Unconcentrated sample

Sample concentrated 100‐foldNotes:
EIC - extracted ion chromatogramm/z - mass-to-charge ratio
SPE - solid-phase extraction

Extracted Ion Chromatograms (m/z 508.9357) of C8HF15O8 in
Stormwater Sample from Location 42
Collected March 17, 2022
Chemours Fayetteville Works, North Carolina

FigureJune 2022

1

Tentative structure: CF3‐O‐CF2‐O‐CF2‐O‐CF2‐O‐CF2‐O‐CF2‐O‐CF2‐COOH

Notes:EIC - extracted ion chromatogramm/z - mass-to-charge ratio
SPE - solid-phase extraction
Tandem Mass Spectrometry Fragmentation Pattern ofC8HF15O8
Chemours Fayetteville Works, North Carolina

FigureJune 2022

2