Extending PFAS Analytical Workflows with APGC-MS/MS Analysis: Analysis of Environmental and Food Packaging Samples

Significance of the topic

Per- and polyfluoroalkyl substances (PFAS) include volatile and semi-volatile precursor classes that are poorly covered by routine LC-MS/MS workflows. These GC-amenable PFAS (e.g., fluorotelomer alcohols, acrylates, methacrylates, acetates, and certain sulfonamides/sulfonamidoethanols) can be mobile in the atmosphere, serve as precursors to persistent perfluoroalkyl carboxylic acids (PFCAs) and sulfonates (PFSAs), and historically were used in food-contact and textile treatments. Expanding analytical capability to include APGC-MS/MS (atmospheric pressure gas chromatography with tandem quadrupole MS) enables detection of these compounds, supports source attribution, reveals transformation pathways during treatment processes, and helps laboratories meet emerging regulatory requirements for food packaging and environmental monitoring.

Objectives and study overview

• Evaluate an APGC-MS/MS workflow targeting 35 GC-amenable PFAS in environmental matrices (wastewater, soil) and paper/paperboard food packaging materials.
• Compare APGC-MS/MS findings with prior LC-MS/MS data to identify precursor transformation to terminal PFAS (PFCAs/PFSAs) in wastewater treatment.
• Assess method sensitivity, robustness, and applicability for regulatory compliance (e.g., EU packaging limit of 25 ng/g or ng/mL) via post-spike experiments.

Used methodology and sample preparation

• Standards and internal standards: native PFAS from commercial suppliers; isotopically labelled I.S. used for quantitation.
• Environmental extracts: samples had been previously prepared following EPA Method 1633A (aqueous, solid, biosolids, tissue) and were initially analyzed by LC-MS/MS. Final extracts were estimated in a solvent mix approximating 94% methanol, 4% water, 1% ammonium hydroxide, 0.6% acetic acid.
• Food packaging: 10 x 10 cm sections of paper/paperboard were cut, weighed, and extracted by sonication in methanol with 1% ammonium hydroxide (20 mL, 1 h). Aliquots were taken for APGC-MS/MS analysis.
• APGC source optimization: proton-transfer ionization conditions established by placing open water vials in the source to provide water vapor, enhancing formation of protonated analyte ions. Autosampler wash solvents included IPA (to reduce sulfonamide carryover) and methanol; pre- and post-injection washes performed.

Used instrumentation

• Gas chromatograph: Agilent 8890 GC with 7693A autosampler.
• Column: Restek Rtx-200, 30 m x 0.25 mm ID, 0.50 µm film.
• Inlet: Siltek deactivated straight liner with wool; pulsed split injection (40 psi, 0.6 min), 10:1 split, 1 µL injection at 240 °C.
• Carrier and makeup gas: Nitrogen (carrier flow 2 mL/min; makeup 300 mL/min).
• APGC source: Waters APGC source with proton-transfer (API+) using water vapor; corona current 1.0 µA; source temp 150 °C; cone/auxiliary gas flows 250/150 L/hr.
• Mass spectrometer: Xevo TQ Absolute triple quadrupole MS operated with argon collision gas in MRM mode; quantitation using waters_connect for Quantitation software.

Main results and discussion

• General performance: The APGC-MS/MS method provided sensitive, well-resolved chromatographic detection of the 35-target panel in matrix extracts, with good peak shape in complex wastewater extracts spiked at 25 ng/mL.
• Wastewater: Influent water contained multiple fluorotelomer alcohols (6:2, 8:2, 10:2, 12:2 FTOH) quantified between ~6.3–219 ng/L. Effluent samples showed substantial removal of most FTOHs, with only 6:2 and 8:2 detected above limits (~2.9 and 2.3 ng/L), indicating partial removal or transformation during treatment.
• Transformation evidence: Comparison with prior LC-MS/MS PFCA results on the same wastewater samples revealed either increases or stable concentrations of C4–C10 PFCAs in effluent relative to influent, consistent with oxidative degradation pathways of FTOHs (e.g., 6:2 FTOH → C4–C6 PFCAs). APGC-MS/MS thus identified incoming precursors that likely contributed to PFCA effluent loads.
• Complementarity with LC-MS/MS: N-MeFOSE and N-EtFOSE were quantified consistently in influent by both techniques, but APGC-MS/MS showed higher sensitivity enabling detection in effluent where LC-MS/MS did not (below its detection limit). This demonstrates APGC's added value for semi-volatile precursors.
• Soil (ski-wax impacted sites): 6:2, 8:2, 10:2 FTOHs were detected in soils collected from downhill and cross-country ski locations. Downhill sites (wax application zones) had roughly an order of magnitude higher 6:2 FTOH than cross-country sites; spatial patterns suggest both localized application and atmospheric deposition contributions.
• Food packaging: Seven paper/paperboard packaging samples (e.g., fry box, sandwich wrapper, plates, cups, bakery bag) showed no detectable levels of the 35 targeted GC-amenable PFAS, consistent with current FDA restrictions and indicative of compliance in this limited sample set.
• Method accuracy and artifacts: Post-spike recovery experiments (2.5–25 ng/mL for environmental extracts; 25 ng/mL for packaging, higher for sulfonamides) demonstrated good accuracy for FTOHs, N-xFOSA, and N-xFOSE. Several intermediate oxidative-pathway compounds (FTAcr, FTMAC, FTOAc) measured lower than expected, likely due to oxidative degradation in the autosampler over time. Sulfonamides exhibited inlet carryover in some runs, inflating apparent concentrations; IPA washes mitigated but did not fully eliminate carryover risk.

Benefits and practical applications

• Provides a sensitive complementary workflow to LC-MS/MS, enabling detection of volatile/semi-volatile PFAS precursors that drive formation of persistent PFCAs/PFSAs.
• Improves source attribution (e.g., identifying incoming precursors at wastewater treatment plants, detecting ski-wax related contamination) and aids in interpreting treatment efficacy and fate processes.
• Suitable for regulatory compliance screening of food-contact materials at concentrations well below the EU limit of 25 ng/g (or ng/mL equivalent in extracts) for targeted PFAS.
• Allows laboratories to expand service offerings beyond routine targeted LC suites, delivering deeper environmental and material assessments.

Future trends and opportunities

• Method optimization to reduce in-line degradation and autosampler-related oxidative losses for unstable intermediates (e.g., automation sequence timing, antioxidant additives, low-temperature autosampler racks).
• Further inter-method harmonization and combined APGC–LC workflows to comprehensively quantify total PFAS burden and transformation fluxes in treatment systems and the atmosphere.
• Expansion of surrogate and isotope-labelled standards for additional GC-amenable PFAS to improve quantitation and reduce matrix effects and carryover bias.
• Application to larger surveillance studies of food packaging, textile-treated materials, and atmospheric monitoring to map long-range transport of volatile precursors.

Conclusion

APGC-MS/MS targeting 35 GC-amenable PFAS proved to be a robust and sensitive complement to LC-MS/MS. The method successfully detected key volatile/semi-volatile precursors (notably FTOHs and some FOSE/ FOSA derivatives) in wastewater and soil, revealed precursor–product relationships consistent with PFCA formation during wastewater treatment, and demonstrated fitness for food packaging screening at regulatory-relevant concentrations. Remaining analytical challenges include oxidative degradation of some intermediates and sulfonamide carryover, but with appropriate QA/QC these can be managed. Combined APGC and LC workflows provide a more complete analytical picture of PFAS occurrence, sources, and fate.

References

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