Analysis of PFAS in indoor air using thermal desorption coupled to gas chromatography – mass spectrometry (TD-GC-MS/MS)

Significance of the topic

Per- and polyfluoroalkyl substances (PFAS) are synthetic compounds widely used in consumer and industrial products due to their water- and oil-repellent properties. Their persistence and health-related risks, including bioaccumulation and links to cancers and endocrine disorders, make monitoring PFAS in indoor air crucial for assessing human exposure and ensuring environmental safety.

Aims and study overview

This application note presents a high-throughput method for simultaneous analysis of 19 PFAS across four functional groups (perfluoroalkyl carboxylic acids, fluorotelomer alcohols, fluorotelomer carboxylic acids, and perfluorooctane sulfonamides) in indoor air using thermal desorption coupled to gas chromatography-tandem mass spectrometry (TD-GC-MS/MS). In addition, PFAS emission rates from a common consumer product—a child’s waterproof coat—were evaluated using a Micro-Chamber/Thermal Extractor (μ-CTE).

Methodology

• Sampling: Air volumes of 20 L (workplace) or 70 L (residential) were drawn at 100 mL/min onto stainless steel sorbent tubes with extended PFAS sorbent beds.
• Standards and calibration: Working standards covering 10–5 000 pg/µL were spiked onto sorbent tubes using a calibration rig and purged to remove solvent, generating six-point linear curves (R² > 0.99).
• Instrument background and blanks: Unexposed traps and blank sorbent tubes showed negligible PFAS background; method detection limits (MDLs) averaged 16 pg on-tube, corresponding to 0.8 ng/m³ for a 20 L sample.
• Emission testing: Fragments of a waterproof coat were placed in the μ-CTE at ambient temperature; emitted vapors were trapped and analyzed to determine compound-specific emission rates.

Instrumentation

• Thermal desorption: Markes International TD100-xr Advanced with Internal Standard Addition/Dry Purge accessory and PFAS focusing trap.
• Gas chromatography: Thermo Scientific TRACE 1610 Series GC with TraceGOLD TG-200MS capillary column (30 m × 0.25 mm × 1.0 μm, trifluoropropylmethylpolysiloxane phase).
• Mass spectrometry: Thermo Scientific TSQ 9610 triple quadrupole MS equipped with Advanced Electron Ionization (AEI) source, operated in combined full-scan (m/z 35–650) and timed-SRM modes for screening and quantification.
• Emission chamber: Markes International Micro-Chamber/Thermal Extractor (μ-CTE) for sampling emissions from solid materials without solvent extraction.

Main results and discussion

• Analytical performance: The TD-GC-MS/MS method provided average MDLs of 0.8 ng/m³, robust linearity, and low carryover without cryogenic cooling.
• Workplace air: Total PFAS concentrations ranged from 38 to 157 ng/m³ across five locations, dominated by perfluoroalkyl carboxylic acids (notably PFOA, PFDoA, PFTeDA) and fluorotelomer alcohols.
• Residential air: Renovation site sampling revealed lower PFAS levels (total ~11 ng/m³) with a different profile favoring fluorotelomer alcohols (FOET, FDET) and octanesulfonamides.
• Consumer product emissions: The child’s waterproof coat emitted primarily 8:2 fluorotelomer ethanol (FOET) at 3.94 ng/g (0.131 ng/g/min) and 10:2 FTOH (FDET) at 0.81 ng/g (0.027 ng/g/min), indicating potential indoor sources of volatile PFAS.

Benefits and practical applications

• High throughput and automation: Sequential analysis of up to 100 tubes with unattended operation and electronic cooling.
• No sample prep solvent: Solid and liquid samples can be analyzed directly, reducing cost and handling risks.
• Built-in quality control: Automated internal standard addition and sorbent re-collection ensure analyte transfer and check for losses.
• Regulatory compliance: Low detection limits support monitoring of PFAS at concentrations relevant to emerging indoor air guidelines.

Future trends and potential applications

• Extension to broader PFAS classes and non-target screening for emerging fluorochemicals in indoor environments.
• Integration with real-time sampling tools and multiplexed detectors for rapid exposure assessment.
• Standardization of emission testing protocols for building materials and consumer products to inform regulatory limits.
• Deployment in occupational hygiene, indoor air quality certification, and longitudinal exposure studies in homes, schools, and offices.

Conclusion

The combined TD100-xr GC-MS/MS workflow provides sensitive, reliable, and high-throughput analysis of volatile and semi-volatile PFAS in indoor air. Coupling with μ-CTE emission testing enables quantification of PFAS release from consumer materials. This approach meets the demands of laboratories and industries seeking comprehensive indoor air monitoring, exposure assessment, and compliance with forthcoming PFAS regulations.

References

1. Agency for Toxic Substances and Disease Registry (ATSDR). Per- and Polyfluoroalkyl Substances (PFAS) and Your Health. 2022.
2. Secretariat of the Basel, Rotterdam and Stockholm Conventions. Perfluorooctanoic acid (PFOA), its salts and PFOA-related compounds – Factsheet. 2020.
3. U.S. Environmental Protection Agency (EPA). Definition and Procedure for the Determination of the Method Detection Limit, Revision 2; EPA 821-R-16-006; 2016.
4. Morales-McDevitt ME et al. The air that we breathe: Neutral and volatile PFAS in indoor air. Environ Sci Technol Lett. 2021;8:897–902.
5. Padilla-Sánchez JA, Papadopoulou E, Poothong S, Haug LS. Investigation of the best approach for assessing human exposure to PFAS through indoor air. Environ Sci Technol. 2017;51:12836–12843.