Putting the (Atmospheric) Pressure on Forever Chemicals: A Targeted Analysis of GC Amenable PFAS using APGC–MS/MS

Significance of the topic

A sensitive and selective analytical capability for gas-chromatography (GC) amenable per- and polyfluoroalkyl substances (PFAS) complements routine liquid chromatography–mass spectrometry (LC–MS) workflows by covering more volatile classes (e.g., fluorotelomer alcohols, acrylates, acetates) that are poorly characterized by LC. Broadening analytical coverage is important for environmental monitoring, food packaging safety, regulatory compliance and understanding PFAS transformation pathways and sources.

Objectives and study overview

This work reports development, optimization and application of a targeted APGC+ (atmospheric pressure gas chromatography) tandem MS method to quantify 35 GC‑amenable PFAS. The goals were to demonstrate improved molecular ion formation compared to electron ionization (EI), establish method limits of quantitation and robustness, adapt sample extracts prepared by EPA 1633 for GC analysis, and evaluate environmental and food packaging samples for the presence of volatile PFAS classes.

Methodology

Sample collection and preparation:

• Environmental matrices: surface and ground water (influent and effluent), soil and fish tissue were extracted following EPA Method 1633A workflows previously applied for LC–MS/MS; final extracts were ~94% methanol, 4% water, 1% ammonium hydroxide and 0.6% acetic acid.
• Food packaging: 10 cm × 10 cm pieces of paper or paperboard were extracted with 20 mL methanol containing 1% ammonium hydroxide, sonicated 1 hour and aliquoted for analysis.

Instrumental and chromatographic approach:

• GC: Agilent 8890 with an ALS autosampler and an Rtx‑200 column (30 m × 0.25 mm × 0.50 µm); carrier gas nitrogen at 2 mL/min; pulsed split injection (10:1), 1 µL injection volume; inlet temperature 240 °C; transfer line ~310 °C; makeup gas N2 ~300 mL/min; temperature program ramping to a high final temperature (~310 °C) for elution of high‑boiling PFAS.
• MS: Waters Xevo TQ Absolute operated with APGC+ ionization (API+, proton transfer using water vapor); corona current 1.0 µA; cone gas 250 L/hr; auxiliary gas 150 L/hr; quantitation with waters_connect software.

Analytical strategy:

• APGC+ was used to promote formation of intact [M+H]+ ions for many target PFAS, increasing sensitivity and selectivity relative to EI which produced extensive fragmentation.
• Calibration standards were prepared in the same final extract solvent composition to match matrix conditions.

Instrumentation used

• GC system: Agilent 8890 with ALS autosampler.
• Column: Rtx‑200, 30 m × 0.25 mm × 0.50 µm.
• Mass spectrometer: Waters Xevo TQ Absolute with APGC+ ion source.
• Carrier and makeup gas: Nitrogen (carrier 2 mL/min, makeup ~300 mL/min).
• Data processing: waters_connect for quantitation.

Main results and discussion

Method sensitivity and chromatographic performance:

• Most target PFAS achieved lower limits of quantitation (LLOQ) in the 0.025–0.1 ng/mL range, illustrating high sensitivity for many analytes when using APGC+.
• Sulfonamide PFAS showed higher LLOQs (approximately 1–5 ng/mL), and x:1 fluorotelomer alcohols (FTOHs) exhibited LLOQs around 5–10 ng/mL.
• APGC+ preserved intact [M+H]+ molecular ions (example: 8:2 FTOH observed as m/z 465), whereas EI spectra were extensively fragmented. The intact molecular ion improves compound identification confidence and quantitative selectivity.
• Chromatographic separation of the 35 compounds was demonstrated in a complex food‑packaging extract spiked at 25 ng/mL, simulating regulatory target concentrations.

Sample analyses and findings:

• Food packaging extracts tested in this study did not contain detectable levels of the targeted GC‑amenable PFAS at the method’s quantitation limits.
• Environmental samples (wastewater influent/effluent, soils, and fish/shrimp tissue) contained detectable and quantifiable amounts of GC‑amenable PFAS. Fluorotelomer alcohols (FTOHs), particularly 6:2 FTOH, were most frequently observed with highest levels in wastewater and ski‑wax‑impacted soils.
• Post‑spike quantitation experiments in a brown paper wrapper generally returned accurate recoveries for most analytes; however, acrylates (FTAcr) and acetates (FTOAc) showed lower than expected recoveries, consistent with known atmospheric or in‑extract degradation pathways.

Benefits and practical applications of the method

• APGC‑MS/MS extends PFAS analytical coverage to volatile and semi‑volatile classes that are not well captured by LC–MS/MS, enabling a more comprehensive PFAS profile of environmental and consumer matrices.
• The technique offers improved specificity through observation of molecular ions, reducing potential interference from matrix‑coeluting fragments common with EI‑based GC methods.
• Adapting extracts from EPA 1633A allows laboratories to leverage existing sample workflows and re‑analyze archived extracts for GC‑amenable PFAS without developing separate extraction pipelines.
• Applicable for environmental monitoring (wastewater, soils, biota), product surveillance (food packaging), and research into PFAS transformation and source attribution.

Limitations and considerations

• Certain PFAS chemistries (e.g., acrylates, acetates) are prone to atmospheric or in‑vial degradation, which can bias quantitation low unless stabilization or rapid analysis is employed.
• Some compound classes (sulfonamides, long‑chain FTOHs) exhibited higher LLOQs, requiring attention to sample concentration and injection strategies for trace-level quantitation.
• Complementary use of LC–MS/MS remains necessary for the full spectrum of PFAS analytes (non‑volatile and ionic species).

Future trends and potential applications

• Expansion of target lists to include more transformation products, precursors and novel volatile PFAS as analytical standards become available.
• Further methodological refinement: improved ionization chemistries, derivatization strategies to stabilize labile analytes, and coupling to high‑resolution MS for non‑target screening.
• Standardization and regulatory method development to harmonize LC and GC approaches for comprehensive PFAS surveillance in environmental and consumer matrices.
• Automation and miniaturization of sample preparation to increase throughput and reduce sample handling‑related losses for labile PFAS.

Conclusion

The APGC+ MS/MS method developed for 35 GC‑amenable PFAS provides sensitive, specific and complementary coverage to LC–MS/MS workflows. APGC’s ability to produce intact molecular ions improves identification and quantitative performance for volatile PFAS classes. Environmental samples contained measurable levels of volatile PFAS (not detected in tested packaging), highlighting the need for combined GC and LC analyses to fully characterize PFAS contamination. Method limitations related to analyte stability and variable LLOQs should be considered when applying the technique in regulatory and monitoring contexts.

Reference summary

The study followed extraction and preparative approaches adapted from EPA 1633A and referenced Waters application notes detailing LC‑MS/MS analyses of aqueous, soil and tissue matrices for PFAS.

References

1. US Environmental Protection Agency. EPA 1633A: Analysis of Per‑ and Polyfluoroalkyl Substances (PFAS) in Aqueous, Solid, Biosolids, and Tissue Samples by LC‑MS/MS. January 2024.
2. Organtini K, Rosnack K, Plummer C, Hancock P, Burt O. Analysis of Per‑ and Polyfluoroalkyl Substances (PFAS) in Accordance with EPA 1633 Part 2: Analysis of Aqueous Matrices. Waters Application Note 720008143. 2024.
3. Organtini K, Rosnack K, Plummer C, Hancock P, Burt O. Analysis of Per‑ and Polyfluoroalkyl Substances (PFAS) in Accordance with EPA 1633 Part 2: Analysis of Soil and Tissue. Waters Application Note 720008230. 2024.