High-throughput analysis of both neutral and ionic PFAS in ambient air using thermal desorption coupled to gas chromatography – mass spectrometry (TD-GC-MS/MS)

Significance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental pollutants with both ionic and neutral forms that travel long distances in the atmosphere, potentially affecting human health and ecosystems. Reliable measurement of airborne PFAS at trace levels is essential for understanding emission sources, transport patterns, and exposure risks.

Objectives and Overview of the Study

This work presents a single, high-throughput method for the simultaneous determination of 19 PFAS analytes—including volatile fluorotelomer alcohols (FTOHs), fluoroalkylsulfonamides (FOSAs), and ionic perfluorocarboxylic acids (PFCAs) and fluorotelomer carboxylic acids (FTCAs)—in ambient air. By coupling thermal desorption (TD) with gas chromatography–tandem mass spectrometry (GC-MS/MS), the study aims to achieve rapid analysis, low detection limits, and minimal sample preparation.

Methodology and Instrumentation

Sampling and Preconcentration:

• Ambient air was drawn through dedicated PFAS sorbent tubes at controlled flow rates (10–500 mL/min) to collect up to 300 L of air per sample.
• Specialized stainless-steel tubes packed with PFAS-optimized sorbent material enable preconcentration of analytes down to single-digit pg/m³ levels.

Thermal Desorption and GC-MS/MS:

• TD system: Markes International TD100-xr Advanced with automated dry purge and Internal Standard Addition/Dry Purge (ISDP) accessory for accurate spiking of deuterated toluene internal standard.
• GC setup: Thermo Scientific TRACE 1610 GC fitted with a TraceGOLD TG-200MS column (30 m × 0.25 mm × 1.0 µm) featuring a trifluoropropylmethyl polysiloxane phase for optimal stability and low bleed.
• MS/MS detection: Thermo Scientific TSQ 9610 triple quadrupole equipped with Advanced Electron Ionization (AEI) source operating in timed-SRM mode for targeted quantification.

Results and Discussion

Method Performance:

• Calibration curves for all 19 PFAS were linear (R² > 0.99) across 10–5 000 pg/µL depending on compound class.
• Method detection limits averaged 31 pg/m³ (based on 300 L air volume), consistent with typical environmental concentrations.
• Blank assessments confirmed minimal background contamination when using PFAS-dedicated tubes and trap conditioning.

Ambient Air Monitoring:

• Samples collected from three sites in a light industrial area revealed widespread detection of short-chain PFCAs (PFBA, PFHxA, PFOA) at the highest levels.
• Re-collection capability allowed paired targeted SRM analysis and full-scan untargeted screening from the same tube.

Benefits and Practical Applications

• Single-run analysis of both neutral and ionic PFAS simplifies workflow and increases laboratory throughput.
• Low detection limits and automated sampling reduce solvent use and manual handling.
• Automated trap re-collection provides analytical redundancy and supports method validation.

Future Trends and Potential Applications

Advancements in PFAS analysis may include expanded untargeted screening libraries, integration of real-time field sampling with portable TD-GC systems, and coupling with high-resolution MS for unknown compound identification. Further miniaturization and automation of sampling accessories could enable large-scale monitoring networks and rapid response to emission events.

Conclusion

The described TD-GC-MS/MS approach provides a robust, high-throughput solution for simultaneous quantification of volatile and ionic PFAS in ambient air. With excellent sensitivity, linearity, and automated workflows, this method supports environmental monitoring, regulatory compliance, and research into PFAS atmospheric behavior.

Instrumentation

• Markes International TD100-xr Advanced thermal desorber with ISDP accessory
• Thermo Scientific TRACE 1610 gas chromatograph
• Thermo Scientific TSQ 9610 triple quadrupole mass spectrometer with AEI source
• TraceGOLD TG-200MS capillary column (30 m × 0.25 mm × 1.0 µm)

References

1. Ellis D.A. et al. Atmospheric Lifetime of Fluorotelomer Alcohols. Environ. Sci. Technol. 2003, 37, 3816–3820.
2. Interstate Technology & Regulatory Council. PFAS Technical and Regulatory Guidance Document. 2020.
3. D’Ambro E.L. et al. Emissions and Deposition of PFAS from a Fluoropolymer Facility. Environ. Sci. Technol. 2021, 55, 862–870.
4. Rauert C. et al. Atmospheric PFAS Trends over Seven Years. Environ. Pollut. 2018, 238, 94–102.
5. U.S. EPA. Definition and Procedure for the Determination of the Method Detection Limit. EPA 821-R-16-006, 2016.