Analysis of Trace Perfluorinated and Polyfluorinated Organic Vapors in Air

Significance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants with diverse industrial applications and environmental persistence. Their volatility and wide chemical variety make air monitoring essential to understand long-range transport, exposure risks, and complete mass balance assessments. Trace-level detection, often at sub-parts per trillion, poses analytical challenges that demand sensitive and robust techniques.

Objectives and Scope of the Study

This study evaluates a cryogen-free thermal desorption (TD) system coupled to gas chromatography/mass spectrometry (GC/MS) for quantifying trace volatile and semivolatile PFAS in air. Key aims include assessing method performance—linearity, sensitivity, repeatability, storage stability—validating quantitative TD sample re-collection, and analyzing real ambient samples from a parking facility.

Methodology and Instrumentation

Analytical workflow:

• Sampling onto Agilent stainless steel material emissions tubes (C-TBME10) with hydrophobic sorbents at 100 mL/min up to 500 L.
• Cryogen-free thermal desorption using Markes TD100-xr: trap cooled to –30 °C, desorption at 300 °C for 12 min, split ratio 6:1.
• GC separation on Agilent J&W VF-200ms column (30 m × 0.25 mm, 1 μm) at 1.2 mL/min constant flow, temperature ramp from 35 °C to 280 °C.
• Detection by Agilent 5977B GC/MSD in EI SIM mode targeting characteristic ions (m/z 131 for PFCAs, 95 for FTOHs, qualifiers m/z 55, 93).

Main Results and Discussion

• Breakthrough volumes: No detectable breakthrough for any target PFAS up to 500 L.
• Storage stability: >90% recovery after 7 days at ambient and 15 days at 5 °C.
• System and tube blanks showed no measurable PFAS background.
• Quantitative TD sample re-collection demonstrated consistent recovery across multiple desorption cycles without artefact formation.
• Linearity: Correlation coefficients (R2) >0.997 over calibration ranges, LODs down to sub-ppt levels.
• Repeatability: Relative standard deviations ≤5% for all analytes.
• Real air samples: PFAS recoveries from spiked parking-garage air exceeded 80%.

Benefits and Practical Applications

Cryogen-free TD-GC/MS offers high sensitivity, compliance with international standards, flexible sample re-analysis, and broad PFAS coverage. The method enables routine monitoring and research applications in environmental, indoor, and occupational air quality assessments.

Future Trends and Applications

Integration with advanced MS technologies (e.g., triple quadrupole, time-of-flight) promises enhanced sensitivity and compound identification. Portable TD systems and novel sorbents may support field deployment and real-time PFAS air monitoring, addressing regulatory and exposure assessment needs.

Conclusion

The combination of cryogen-free TD100-xr and Agilent 8890/5977B GC/MSD delivers robust, sensitive, and reproducible trace analysis of a diverse PFAS suite in air. This approach meets stringent detection requirements and offers practical advantages for environmental monitoring.

References

• EN ISO 16017: Indoor, Ambient and Workplace Air – Sampling and Analysis of Volatile Organic Compounds by Sorbent Tube/Thermal Desorption/Capillary GC – Part 1.
• US EPA TO-17: Determination of Volatile Organic Compounds in Ambient Air Using Active Sampling onto Sorbent Tubes.
• ISO 16000-6: Indoor Air – Determination of Organic Compounds in Indoor and Test Chamber Air by Active Sampling on Sorbent Tubes.
• ASTM D6196: Standard Practice for Choosing Sorbents and Thermal Desorption Analytical Conditions for Monitoring VOCs.
• HJ 759: Ambient Air. Determination of VOCs Collected by Specially-Prepared Canisters and Analyzed by GC/MS.
• Stockholm Convention on Persistent Organic Pollutants.
• S. Nakayama et al., Worldwide Trends in Tracing PFAS in the Environment. Trends in Analytical Chemistry 2019, 121, 115410.
• PFAS Analysis in Water | Agilent.
• PFAS Analysis by LC/MS/MS, PFAS Testing, eMethod | Agilent.