Application of a chemical ionization mass spectrometer to gas-phase PFAS measurements

Theran Riedel

United States Environmental Protection Agency

Office of Research and Development

Center for Environmental Measurement and Modeling

Air Methods and Characterization DivisionCombustion Sources Branch

A&WMA Information Exchange

December 4, 2019

Collaborators

2

Center for Public Health & Environmental Assessment

Public Health & Environmental Systems Division

Exposure Indicators Branch

-Andy Lindstrom

Jacobs Technology-Bill Preston

Arcadis-Johnsie Lang

Center for Environmental Measurement & Modeling

Air Methods & Characterization Division

Combustion Sources Branch

-Jeff Ryan-Bill Linak-CW Lee-Ken Krebs-Erin Shields

Atmospheric & Environmental Systems Modeling Division

Atmospheric Chemistry & Aerosols Branch

-John Offenberg

Watershed & Ecosystem Characterization Division

Multimedia Methods Branch

-Mark Strynar-James McCord

Outline

• PFAS overview

• Introduction to the measurement technique

• Application potential to current PFAS projects

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PFAS interest at EPA

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• Involved in fluoropolymer manufacturing and materials application processes

• Releases of PFAS into the environment:• Aqueous film forming foam (AFFF) – firefighting foams

• Industrial emissions

• Landfills and leachates

• Wastewater treatment effluent and land application of biosolids

• Potential persistent organic pollutant with health effects only known for a few compounds

• Most PFAS are measured in the condensed phase (water samples) through offline analysis

• High fluorine content means high volatility (gas-phase)• 10:2 fluorotelomer alcohol (C12F21H5O) has a vapor pressure 500x that of

equivalent hydrocarbon dodecan-1-ol (C12H26O)

Perfluorooctanoic Acid (PFOA)

2,3,3,3-tetrafluoro-2-heptafluoropropoxypropanoic acid(GenX; HFPO-DA)

PFAS in air

5Davis et al. Chemosphere 67 (2007) 2011–2019

PFAS deposition from air

6Source: Ohio State University

Outline

• PFAS overview

• Introduction to the measurement technique• Chemical ionization mass spectrometry (CIMS)

• Application potential to current PFAS projects

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CIMS

High Resolution Time of Flight Chemical Ionization Mass Spectrometer

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Direct ambient air sampling · no collection, extraction, pre-concentration, or derivatization

Field deployable (needs shelter and power source)

Parts per trillion (by volume) detection limits

Approximate mass range: 1 – 1100 Da

Measurement rate: ~1 Hz

Sample draw: ~1.5 slpm

Analyte gases detected as cluster with iodide (m/z 126.905)

Aerodyne/TOFWERK ToF-CIMS

CIMS

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Iodide reagent ion chemistry

CH3I(g) + → I- + CH3+

R(g) + I- → I-·R

Example (formic acid):H2CO2(g) + I- → I-·H2CO246.005 + 126.905 → 172.910

- Soft ionization

- Iodide has large negative mass defect

- CIMS most sensitive to species with significant dipole

(polar molecules – acids, alcohols)

High Resolution Time of Flight Chemical Ionization Mass Spectrometer

Example CIMS Mass Spectra

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Outline

• PFAS overview

• Introduction to the measurement technique• Chemical ionization mass spectrometry (CIMS)

• Application potential to current PFAS projects• Detection of relevant PFAS

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Detection of Fluorotelomer Alcohols (FTOHs)

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• Fluorotelomer alcohols used in manufacturing and are degradation product of other PFAS

• Largely unmeasured in the gas-phase

Generic formula: F(CF2)nCH2CH2OH (n = 4, 6, 8, etc.)

Expected Mass:4:2 FTOH + I- = m/z 390.9247(6.6% isotope at m/z 391.9281)

Detection of FTOHs

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FTOH generic formula: F(CF2)nCH2CH2OH

(6:2 FTOH: 2.1 pptv ≈ 31 ng/m3)

(8:2 FTOH)

FTOH calibrations

Detection of PF carboxylic acids

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• Also used in fluoropolymer manufacturing

• Atmospheric degradation products of FTOHs

• Largely unmeasured in the gas-phase

Perfluorooctanoic Acid (PFOA)2,3,3,3-tetrafluoro-2-heptafluoropropoxypropanoic acid

(GenX; HFPO-DA)

Outline

• PFAS overview

• Introduction to the measurement technique• Chemical ionization mass spectrometry (CIMS)

• Application potential to current PFAS projects• Detection of relevant PFAS

• Condensed-phase headspace sampling

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Volatilization and headspace analysis

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• Condensed-phase samples can also be analyzed by slow volatilization and headspace sampling

• Dispersions (used for fluoropolymer coating applications) and AFFF have been sampled in this way

PFAS dispersion sampling for 10:2 FTOH

Non-targeted analysis – dispersions

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Outline

• PFAS overview

• Introduction to the measurement technique• Chemical ionization mass spectrometry (CIMS)

• Application potential to current PFAS projects• Detection of relevant PFAS

• Condensed-phase headspace sampling

• Stack sampling and process monitoring

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SUMMA canister analysis of stack samples

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• Offline analysis of SUMMA canister samples

• Targeted (alcohols and acids) and non-targeted

• Quick data turnaround (~1 day)

SUMMA canister stack sample collection

Direct stack sampling

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Process monitoring:

CIMS at PTFE curing facility

Outline

• PFAS overview

• Introduction to the measurement technique• Chemical ionization mass spectrometry (CIMS)

• Application potential to current PFAS projects• Detection of relevant PFAS

• Condensed-phase headspace sampling

• Stack sampling and process monitoring

• Assessment of PFAS destruction methods

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Assessment of PFAS destruction methods

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• Detection of PFAS gas-phase starting material (like PFOA, HFPO-DA, FTOHs, etc.)

• Monitor the efficiency of starting material destruction and potential products

• Evaluate destruction/removal efficiencies (DREs) of the treatment process

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The views expressed in this presentation are those of the author and do not necessarily represent the views or policies of the U.S. Environmental Protection Agency. Any mention of trade names, products, or services does not imply an endorsement by the US Government or the United States Environmental Protection Agency. EPA does not endorse any commercial products, services, or enterprises.

The End

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