HomeMy WebLinkAbout2021.12.23_CCO.p11a_PFAS Non-Targeted Analysis and Methods - Interim Report 4
The Chemours Company Fayetteville Works 22828 NC Highway 87 W Fayetteville, NC 28306
PFAS NON-TARGETED ANALYSIS AND
METHODS INTERIM REPORT #4
Process and Non-Process Wastewater and Stormwater
Prepared by
The Chemours Company FC, LLC
Fayetteville Works
22828 NC Highway 87 W
Fayetteville, NC 28306
December 22, 2021
The Chemours Company Fayetteville Works 22828 NC Highway 87 W Fayetteville, NC 28306
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TABLE OF CONTENTS
1 INTRODUCTION ...............................................................................................................1
2 INVESTIGATION OF THE NEXT FIVE MOST ABUNDANT UNKNOWN PFAS IN
GENERAL FACILITY DISCHARGE SAMPLES .............................................................3
3 INVESTIGATION OF THE FIVE MOST ABUNDANT UNKNOWN PFAS IN
CHEMOURS PROCESS WASTEWATER SAMPLES .....................................................5
4 SUMMARY AND NEXT STEPS .......................................................................................5
5 REFERENCES ....................................................................................................................6
The Chemours Company Fayetteville Works 22828 NC Highway 87 W Fayetteville, NC 28306
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LIST OF TABLES
Table 1: Status of Unknown PFAS - Interim Report #4
LIST OF FIGURES
Figure 1: Total Ion Chromatograms and Extracted Ion Chromatograms (m/z 508.9357) of
C8HF15O8 in December 2021 and March 2020 Analyses of Sample from Location
42
Figure 2: Detection of Deprotonated C8HF15O8 and Bicarbonate Adduct of C8HF15O8
Figure 3: Extracted Ion Chromatograms (m/z 508.9357) of Four Sample Bottles from
Location 42 Analyzed in December 2021
Figure 4: Total Ion Chromatograms and Extracted Ion Chromatograms (m/z 508.9357) of
C8HF15O8 in December 2021 and March 2020 Analyses of Sample from Location
16
Figure 5: Extracted Ion Chromatogram for "C4H2F6O2"
Figure 6: MS/MS Fragmentation of R-EVE Standard and of C8HF13O4 in Sample from
Location 42
Figure 7: Extracted Ion Chromatogram for "C4HF9O2S"
Figure 8: MS/MS Fragmentation of "C6H3F7O2"
The Chemours Company Fayetteville Works 22828 NC Highway 87 W Fayetteville, NC 28306
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ACRONYMS AND ABBREVIATIONS
CFRW Cape Fear River Watch
Chemours The Chemours Company FC, LLC
Da dalton
EIC extracted ion chromatogram
Facility Chemours Fayetteville Works, North Carolina
LC liquid chromatography
MS mass spectrometry
MS-MS tandem mass spectrometry
m/z mass-to-charge ratio
NCDEQ NC Department of Environmental Quality
PFAS per- and polyfluoroalkyl substances
QToF quadrupole time-of-flight
TFA trifluoroacetate
The Chemours Company Fayetteville Works 22828 NC Highway 87 W Fayetteville, NC 28306
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1 INTRODUCTION
This fourth 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., non-contact 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 of Environmental 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 in samples 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 fourth interim
report.
First Interim Report
In the first interim report (Chemours, 2020a), the five most abundant unknown PFAS in General
Facility Discharge samples (samples of stormwater, treated non-Chemours process wastewater
and/or non-contact cooling water discharging to the Cape Fear River) and in Chemours Process
Wastewater samples (samples of process wastewater from Chemours manufacturing areas) were
identified using liquid chromatography (LC) coupled to high-resolution quadrupole time-of-flight
(QToF) mass spectrometry. The five most abundant unknown PFAS in the General Facility
Discharge samples were identified as C4H5F3O2, C4H2F4O2, C6H6F6O2, C8H7F9O2 and C10H8F12O2.
The five most abundant unknown PFAS in the Chemours Process Wastewater samples were
identified as C8H2F14O7S, C8HF13O4, C8H5F13O6S, C9H2F14O6 and C6HF11O4. None of the
identified five potential PFAS compounds in the General Facility Discharge samples were
represented in the five potential PFAS compounds in the Chemours Process Wastewater samples.
These ten (10) unknown PFAS were advanced to the next step in the program - identifying
molecular structures.
Second Interim Report
In the second interim report (Chemours, 2020b), investigation into the five most abundant
unknown PFAS in the General Facility Discharge samples revealed that four of the compounds
(C4H5F3O2, C6H6F6O2, C8H7F9O2 and C10H8F12O2) coeluted from the LC. These compounds have
different molecular weights and were therefore expected to be chromatographically resolved.
Examination of the empirical formulas showed that the 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 four compounds may represent a single compound,
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C4H5F3O2, which, upon elution from the LC, undergoes adduction1 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 the QToF mass spectrometer.
In the second interim report (Chemours, 2020b), investigation into the five most abundant
unknown PFAS in the Chemours Process Wastewater samples concluded:
• C8H2F14O7S: the structure was determined to be CF3-CF(COOH)-O-CF2-CF(CF3)-O-
CF2-CF2-SO3H
• C8HF13O4: a structure was tentatively identified for this unknown PFAS, however,
background interference in the samples had to date interfered with confirmation of the
tentatively identified structure
• C8H5F13O6S: the structure was determined to be HO3S-CF2-CF2-O-CF(CF3)-CF2-O-CHF-
CF2-OCH3
• C9H2F14O6: the structure was tentatively determined to be HOOC-CF2-CF2-O-CF(CF3)-
CF2-O-CF(CF3)-COOH
• C6HF11O4: a structure was not yet identified; background contamination in the samples
had to date interfered with confirmation of a tentatively identified structure.
Third Interim Report
The third interim report (Chemours, 2021) showed that the five most abundant unknown “PFAS”
in the General Facility Discharge samples were sodium or potassium adducts of acetate clusters,
containing no fluorine, rather than PFAS. They were therefore eliminated from the list of unknown
PFAS.
The third interim report (Chemours, 2021) showed that, of 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 structure was found to not match an existing authentic standard,
and therefore another structure needs to be proposed; and
• C6HF11O4 was tentatively identified as CF3-O-CF2-O-CF2-CF2-CF2-COOH.
This fourth interim report provides an update on the initial assessment of the second five most
abundant unknown PFAS in the General Facility Discharge samples (of the original top five) and
on efforts to further identify the structures of the four most abundant unknown PFAS in the
Chemours Process Wastewater samples.
1 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.
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The remainder of this report consists of:
• Section 2: Investigation of the Next Five Most Abundant Unknown PFAS in General
Facility Discharge Samples
• Section 3: Investigation of the Five Most Abundant Unknown PFAS in Chemours Process
Wastewater Samples; and
• Section 4: Summary and Next Steps.
2 Investigation of the Next Five Most Abundant Unknown PFAS in General Facility
Discharge Samples
Results of the work conducted on the next five most abundant PFAS in the General Facility
Discharge samples during July-December 2021 are described below and summarized in Table 1.
C8HF15O8 (mass to charge ratio 508.9357)
The compound with the initially suggested empirical formula of C8HF15O8 was seen in the General
Facility Discharge sample from Location 42 when the sample was analyzed in March 2020.
However, when the sample was re-analyzed in December 2021, the compound was not detected
(Figure 1).
The blank run just prior to the March 2020 analysis of the sample from Location 42 did not contain
C8HF15O8; therefore, the presence of C8HF15O8 in the sample was not a result of carryover from a
previous analysis.
The mass spectrum of C8HF15O8 from March 2020 shows the presence of both the deprotonated
compound (C8F15O8-) and the bicarbonate adduct (C8HF15O8•HCO3-), confirming that the
C8HF15O8 itself is not the result of fragmentation of another compound in the ion source of the
mass spectrometer (Figure 2). This bicarbonate anion adduct is usually seen in the analysis of per-
and polyfluoroalkyl carboxylic acids and per- and polyfluoroalkyl ether carboxylic acids. The
bicarbonate likely originates from dissolved carbon dioxide.
The sample from Location 42 consisted of four sample bottles. All four sample bottles were
analyzed, with the same result that the compound was not detected; the possibility that the
compound was present in one sample bottle but not another was therefore discounted (Figure 3).
C8HF15O8 had not been detected initially (in March 2020) in any other General Facility Discharge
locations; however, it had been detected initially in the sample from Location 16 (a Chemours
Process Wastewater location). When the sample from Location 16 was re-analyzed in December
2021, C8HF15O8 was also not detected (Figure 4).
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“C4H2F6O2” (mass-to-charge ratio 194.9884)
The compound with the initially suggested empirical formula of C4H2F6O2 was shown to fragment
to acetate and trifluoroacetate (TFA) and was therefore concluded to be a cluster consisting of an
acetate ion, a sodium ion and a TFA ion, which formed in the ion source of the mass spectrometer.
The correct empirical formula of this compound, therefore, is C4H4F3O4Na and not C4H2F6O2.
This was further supported by the presence of ion masses corresponding to TFA, a
potassium/acetate/TFA cluster, a sodium/TFA dimer cluster and a potassium/TFA dimer cluster
(Figure 5).
As was shown clearly in Interim Report #3, organic anions (such as acetate and TFA) along with
sodium and potassium ions can combine in the ion source of the mass spectrometer to generate ion
clusters that correspond to the mass-to-charge ratio of unknown compounds that can be
misinterpreted to contain fluorine because the algorithm used to determine empirical formulas
during the non-targeted analysis is not exact. This is a known limitation of the negative mass defect
approach used in the algorithm. Fluorine, oxygen and sodium all have negative mass defects, and
the unknown compound, containing both oxygen and sodium, was mistakenly flagged as
fluorinated.
C8HF13O4 (mass-to-charge ratio 406.9596)
The compound with the initially suggested empirical formula of C8HF13O4 was shown to be R-
EVE via standard confirmation (accurate mass and MS/MS fragmentation pattern; Figure 6). R-
EVE (Chemical Abstracts Service Number 2416366-22-6) has previously been identified as a Site-
related PFAS and is found on the Table 3+ analyte list.
“C4HF9O2S” (mass-to-charge ratio 282.9471)
The compound with the initially suggested empirical formula of C4HF9O2S was shown to fragment
to acetate and sulfate and was therefore concluded to be a cluster of two acetate ions, three sodium
ion and a sulfate ion (SO42-), which formed in the ion source of the mass spectrometer. The correct
empirical formula of this compound, therefore, is C4H7SO8Na3 and not C4HF9O2S. This was
further supported by the presence of ion masses corresponding to bisulfate (HSO4-), a cluster of
two sodium ions, an acetate ion and a sulfate ion and a cluster of four sodium ions, three acetate
ions and a sulfate ion (Figure 7).
Sodium ions, sulfate and acetate combined in the ion source of the mass spectrometer to generate
salts of the adduct corresponding to the mass-to-charge ratio of this compound. The compound is
not fluorinated and, therefore, is not a PFAS.
“C6H3F7O2” (mass-to-charge ratio 238.9937)
The compound with the initially suggested empirical formula of C6H3F7O2 was shown to fragment
to acetate and was therefore concluded to be a cluster of a sodium ion, a potassium ion, and three
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acetate ions. The correct empirical formula of this compound, therefore, is C6H10O6NaK and not
C6H3F7O2. This was further supported by the presence of an ion mass corresponding to a cluster
containing two acetate ions and a sodium ion (Figure 8).
Sodium ions, potassium ions and acetate combined in the ion source of the mass spectrometer to
generate a cluster ion corresponding to the mass-to-charge ratio of this compound. The compound
is not fluorinated and, therefore, is not a PFAS.
3 Investigation of the Five Most Abundant Unknown PFAS in Chemours Process
Wastewater Samples
Of the five most abundant PFAS in samples from Chemours Process Wastewater:
• three compounds had previously tentatively identified structures. Synthesis of authentic
standards for these compounds is the next step. Synthetic pathways are under
consideration.
• one compound had a previously tentatively identified structure, which was found to be
incorrect upon comparison to an existing authentic standard. A revised tentatively
identified structure is being developed.
• one compound had previously been identified as EVE Acid, and no further work is required
for this compound.
The current status of the five most abundant PFAS in the Chemours Process Wastewater samples
are summarized in Table 1.
4 SUMMARY AND NEXT STEPS
A summary of the next steps for the potential unknown PFAS discussed in this interim report is
provided below and in Table 1.
Of the next five most abundant unknown “PFAS” in the General Facility Discharge samples, one
compound (C8HF15O8) was not detected in the samples where it had been previously detected.
Further investigation into this compound will be conducted by collecting a new sample from
Location 42 (during a rain event, as had been done previously). The new sample will be analyzed
for the presence of C8HF15O8, and, if found, the sample will be analyzed several times over a
period of months to see if the compound remains stable. The remaining four compounds were
successfully identified (one as R-EVE, one as an adduct of TFA, and two as adducts of acetate that
do not contain fluorine and are not PFAS).
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Of the five most abundant unknown PFAS in the Chemours Process Wastewater samples,
synthesis of authentic standards for three of compounds is the next step. Synthetic pathways,
which are expected to be challenging, are under consideration. A tentatively identified structure
for the fourth unidentified compound, C8H5F13O6S, is being developed. The fifth compound had
previously been identified as EVE Acid and does not require additional work.
5 REFERENCES
Chemours, 2021. PFAS Non-Targeted Analysis and Methods Interim Report #3. July 30, 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.
TABLE 1STATUS OF UNKNOWN PFAS - INTERIM REPORT #4Chemours Fayetteville Works, North CarolinaInitially SuggestedRevised142.0241 141.0168C4H5F3O2*C4H7O4Na157.9983 156.9910C4H2F4O2*C4H6O4K224.0272 223.0199C6H6F6O2*C6H10O6Na2306.0302 305.0230C8H7F9O2*C8H13O8Na3388.0331 387.0258C10H8F12O2*C10H16O10Na4509.9432 508.9357C8HF15O8--Compound no longer detected in original samples.Collect new sample from Location 42 during a rain event to investigate presence and temporal stability of this compound195.9956 194.9884C4H2F6O2*C4H4F3O4NaStructure identified as sodium salt of TFA and acetate adduct. Correct formula is C4H4F3O4NaNone407.9670 406.9596C8HF13O4--Identified as R-EVE None283.9544 282.9471C4HF9O2S* C4H7SO8Na3Structure identified as sodium salt of sulfuric acid and acetate dimer adduct. Correct formula is C4H7SO8Na3. This compound is not a PFAS.None240.0010 238.9937C6H3F7O2*C6H10O6NaKStructure identified as sodium and potassium salt of acetate dimer. Correct formula is C6H10O6NaK. This compound is not a PFAS.None507.9302 506.9229C8H2F14O7S--Structure tentatively identified:CF3-CF(COOH)-O-CF2-CF(CF3)-O-CF2-CF2-SO3HSynthesis of an authentic standard for this compound is under consideration.407.9670 406.9598C8HF13O4--Identified as EVE Acidin Interim Report #3 (July 2021)None475.9587 474.9515C8H5F13O6S--No tentatively identified structure yet Continue to develop a tentatively identified structure471.9630 470.9556C9H2F14O6--Structure tentatively identified:HOOC-CF2-CF2-O-CF(CF3)-CF2-O-CF(CF3)-COOHSynthesis of an authentic standard for this compound is under consideration.345.9693 344.9620C6HF11O4--Structure tentatively identified:CF3-O-CF2-O-CF2-CF2-CF2-COOHSynthesis of an authentic standard for this compound is under consideration.Notes:* - empirical formula initially suggested 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 as determined during January-June 2021 work- further investigation not required as determined during July-December 2021 workC - carbon LC - liquid chromatographDa - dalton MS - mass spectrometerF - fluorine O - oxygenH - hydrogen PFAS - per- and polyfluoroalkyl substancesS - sulfurChemours Process WastewaterGeneral Facility DischargeEmpirical FormulaSample SourceMass(Da)Mass toCharge Ratio(m/z)Structures identified as sodium or potassium adducts of acetate clusters; these are formed in the MS source from sodium or potassium present in the sample matrix and acetate from the LC eluent buffer.Compounds are not PFAS.None.Chemours will commence investigating the next five unknown PFAS in the General Facility Discharge samples; however, their low concentration reduces the possibility of identifying potential structures. Identified Structure Next Steps December 2021
Notes:EIC - extracted ion chromatogram for mass-to-charge ratio of 508.9357TIC - total ion chromatogramm/z - mass-to-charge ratioFigure1December 2021Total Ion Chromatograms and Extracted Ion Chromatograms (m/z 508.9357) of C8HF15O8 in December 2021 and March 2020 Analyses of Sample from Location 42Chemours Fayetteville Works, North CarolinaTIC (STW-LOC 42 run in Dec 2021)TIC (STW-LOC 42 run in Mar 2020)EIC @ 508.9357 (STW-LOC 42 run in Mar 2020)EIC @ 508.9357 (STW-LOC 42 run in Dec 2021)Peak disappears in Dec 2021 run
Notes:EIC - extracted ion chromatogramHCO3- - bicarbonateDetection of Deprotonated C8HF15O8 and Bicarbonate Adduct of C8HF15O8Chemours Fayetteville Works, North CarolinaFigure2December 2021C8F15O8-C8HF15O8+HCO3-
Notes:EIC - extracted ion chromatogram for mass-to-charge ratio of 508.9357 Extracted Ion Chromatograms (m/z 508.9357) of Four Sample Bottles from Location 42 Analyzed in December 2021Chemours Fayetteville Works, North CarolinaFigure3December 2021Bottle 3Bottle 4Bottle 2Bottle 1
Notes:EIC - extracted ion chromatogram for mass-to-charge ratio of 508.9357TIC - total ion chromatogramTotal Ion Chromatograms and Extracted Ion Chromatograms (m/z 508.9357) of C8HF15O8 in December 2021 and March 2020 Analyses of Sample from Location 16Chemours Fayetteville Works, North CarolinaFigure4December 2021TIC (December 2021)TIC (March 2020)EIC @ 508.9357 (December 2021)EIC @ 508.9357 (March 2021)Peak disappears in Dec 2021 run
Notes:CH3COO- - acetateCF3COO- - trifluoroacetateK+ - potassium ionNa+ - sodium ionExtracted Ion Chromatogram for "C4H2F6O2"Chemours Fayetteville Works, North CarolinaFigure5December 2021CH3COO-CF3COO-(CF3COO-+CH3COO-)+Na+(CF3COO-+CH3COO-)+K+(CF3COO-)2+Na+(CF3COO-)2+K+
MS/MS Fragmentation of R-EVE Standard and of C8HF13O4 in Sample from Location 42Chemours Fayetteville Works, North CarolinaFigure6December 2021R-EVE StandardC8HF13O4in Sample from Location 42
Notes:CH3COO- - acetateHSO4- - bisulfateNa+ - sodium ionSO42- - sulfateExtracted Ion Chromatogram for "C4HF9O2S"Chemours Fayetteville Works, North CarolinaFigure7December 2021CH3COO-HSO4-96.9603(SO42-+CH3COO-)+2Na+(SO42-+2CH3COO-)+3Na+(SO42-+3CH3COO-)+4Na+
Notes:CH3COO- - acetateK+ - potassium ionNa+ - sodium ionExtracted Ion Chromatogram for "C6H3F7O2"Chemours Fayetteville Works, North CarolinaFigure8December 2021CH3COO-(CH3COO-)2+Na+(CH3COO-)3+Na+K+238.9937