Comprehensive PFAS screening in food contact materials using combustion ion chromatography and high-resolution mass spectrometry

Significance of the topic

This work addresses comprehensive screening of per- and polyfluoroalkyl substances (PFAS) in food contact materials (FCM) by combining combustion ion chromatography (CIC) for fluorine mass-balance measurements and non-targeted liquid chromatography–high-resolution mass spectrometry (LC–HRMS) for molecular-level identification. Accurate quantification of fluorinated content in FCM is critical for exposure assessment and regulatory compliance (e.g., California’s 100 ppm TOF threshold) because many PFAS are persistent, bioaccumulative, and potentially toxic. CIC provides a global measure of fluorine species that complements targeted and extraction-based mass spectrometric approaches, which often miss non-extractable or strongly bound fluorinated compounds.

Objectives and study overview

The primary objectives were to (1) establish CIC-based workflows to measure total fluorine (TF), total inorganic fluorine (TIF), total organic fluorine (TOF = TF − TIF), and extractable organic fluorine (EOF) in FCM; (2) determine method sensitivity and applicability to representative FCM; and (3) characterize extractable PFAS using non-targeted LC–HRMS to link fluorine mass-balance results with molecular identifications. Eight fiber-based FCM samples (compostable bowls, bakery bags, plates, wraps, pizza boxes, etc.) were cryo-ground, analyzed by CIC for TF/TIF/TOF/EOF, and EOF extracts were interrogated by LC–HRMS with data-dependent MS/MS to annotate PFAS species.

Used methodology and instrumentation

The analytical workflow combined CIC and LC–HRMS with the following key elements:

• Sample preparation: FCM pieces were cryogenically ground (SPEX Freezer/Mill model 6770) to improve homogeneity and extraction efficiency.
• CIC analysis: Samples (10–50 mg) combusted under oxygen/argon; combustion products absorbed in water; fluoride separated by anion-exchange ion chromatography using a Thermo Scientific Dionex IonPac AS24 column (AG24 guard) with hydroxide eluent and suppressed conductivity detection.
• Quantitation strategy: TF measured from combusted sample; TIF determined by direct aqueous injection of water extracts; TOF = TF − TIF; EOF measured after accelerated solvent extraction (ASE) of ground samples using 80% methanol / 20% acetonitrile followed by CIC analysis of extracts.
• LC–HRMS: Thermo Scientific Vanquish Flex UHPLC coupled to an Orbitrap Exploris 240; reversed-phase C18 separation; heated electrospray ionization in negative ion mode; full-scan high resolution (240,000 FWHM at m/z 200) with top-N data-dependent MS/MS (ddMS2) using stepped collision energies.
• Data processing: CIC data processed in Chromeleon CDS; LC–HRMS feature detection and annotation performed with Thermo Scientific Compound Discoverer using spectral libraries (mzCloud, NIST), PFAS-specific mass lists, and in silico fragmentation to support identifications.

Main results and discussion

Key analytical performance and findings:

• Method sensitivity: CIC-based TOF limit of detection was 1.86 ppm, sufficient for current regulatory thresholds.
• Sample fluorine distribution: Among eight FCM samples, three showed very high TOF (≈1082–2142 ppm), well above the 100 ppm regulatory limit; inorganic fluorine was negligible in those high-TOF samples.
• Extractability: EOF represented only a small fraction of TOF in high-TOF samples (~3–13%), indicating that the majority of organofluorine in these materials is non-extractable or strongly bound (e.g., polymeric fluorinated species or matrix-incorporated fluorinated components).
• LC–HRMS identifications: Non-targeted analysis of EOF extracts yielded annotation of 46 PFAS spanning multiple classes, with perfluorocarboxylic acids (PFCAs) most abundant. Both fully perfluorinated terminal compounds and polyfluorinated precursors were observed, suggesting mixed sources and chemistries in FCM formulations.
• Mass-balance implications: LC–HRMS captured only a portion of EOF and thus a small fraction of TOF; the large difference between TOF and EOF highlights limitations of extraction-based LC–MS screening alone for comprehensive PFAS assessment in FCM.
• Method transferability: The TOF workflow was reproduced on a Thermo Scientific Cindion CIC system with TOF values within 98–101% of the original combustion-IC configuration, demonstrating robustness and platform transferability.

Benefits and practical applications of the method

The combined CIC + LC–HRMS approach offers complementary strengths:

• CIC provides a quantitative, matrix-agnostic assessment of fluorine species (TF, TIF, TOF, EOF) that is suitable for regulatory screening and mass-balance evaluation.
• EOF assessment identifies the solvent-extractable fraction relevant for migration/exposure potential, while TOF quantifies the total organofluorine burden, including non-extractable polymeric forms.
• Non-targeted LC–HRMS supplies molecular-level identification of extractable PFAS, informing source attribution, treatment decisions, and targeted monitoring campaigns.
• The approach supports regulatory compliance testing, product stewardship, and risk assessment by revealing whether extractable PFAS explain observed TOF or if hidden (non-extractable) fluorinated materials dominate.

Future trends and potential applications

Anticipated directions and opportunities include:

• Wider adoption of CIC mass-balance workflows in regulatory and industrial laboratories for screening FCM and other matrices (textiles, coatings) where non-extractable organofluorine may be present.
• Improved extraction strategies and complementary techniques (e.g., pyrolysis-GC–MS, size-exclusion fractionation, targeted polymer analysis) to better characterize polymeric or matrix-bound fluorinated species that escape solvent extraction.
• Expansion of non-targeted LC–HRMS libraries and in silico fragmentation models to increase confidence in PFAS annotation and to cover emerging PFAS chemistries and precursors.
• Development of standardized TOF/EOF reporting frameworks and interlaboratory validation to support harmonized regulatory limits and lab accreditation.
• Integration of CIC-derived fluorine data with exposure and toxicological models to prioritize materials and compounds for substitution or restriction.

Conclusions

Combustion ion chromatography combined with non-targeted LC–HRMS provides a powerful, complementary workflow for comprehensive PFAS screening in food contact materials. CIC-derived TOF and EOF measurements reveal that most organofluorine in high-fluorine FCM can be non-extractable and thus invisible to conventional extraction-based LC–MS screening. LC–HRMS successfully annotates a diverse set of extractable PFAS but accounts for only a fraction of the total organofluorine mass. The methodology demonstrates sufficient sensitivity for regulatory thresholds and is transferable across CIC platforms, supporting its application in regulatory screening, product evaluation, and further research into non-extractable fluorinated materials.

Instrumentation used

Instruments and key consumables reported in the study:

• Thermo Scientific Dionex Integrion HPIC system with Dionex IonPac AS24 anion-exchange column (AG24 guard) and suppressed conductivity detection for fluoride separation.
• Nittoseiko Automatic Combustion Unit Model AQF-2100H (combustion unit) and Thermo Scientific Cindion CIC system (method transfer demonstration).
• Thermo Scientific Vanquish Flex UHPLC coupled to an Orbitrap Exploris 240 mass spectrometer with HESI source for LC–HRMS analyses.
• SPEX SamplePrep Freezer/Mill model 6770 for cryogenic grinding of samples.

Reference

1. Hu, J.; Cochran, R. E.; Grim, C. M.; Rumachik, N. G. Comprehensive Screening of PFAS in Food Contact Materials Using Combustion Ion Chromatography for TOF Analysis. Journal of AOAC International, 2025.
2. Hu, J.; Rumachik, N. Application Proof Note 003822: TOF determination using the Cindion CIC system. Thermo Fisher Scientific, 2025.