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In Situ NMR Tube Extraction Reveals Increased Fluorine Release with Polymer Swelling
Mitchell L Kim-Fu1, Isabelle E Logan2, Johanna Peeters Weem3
1Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, United States.
Analytical Chemistry
|April 20, 2026
Summary
A novel in situ nuclear magnetic resonance (NMR) method quantifies extracted fluorine from polymers like Viton A. Acetone showed higher extraction efficiency than methanol, but results require confirmation for individual PFAS analysis.
Area of Science:
- Analytical Chemistry
- Materials Science
- Spectroscopy
Background:
- Quantifying extracted fluorine from fluoropolymers is crucial for environmental and material analysis.
- Traditional methods often require extensive sample preparation, limiting in situ applications.
- Understanding polymer swelling is key to optimizing extraction efficiency.
Purpose of the Study:
- To develop and validate an in situ nuclear magnetic resonance (NMR) technique for quantifying extracted fluorine from fluoropolymers.
- To investigate the relationship between polymer swelling and fluorine extraction efficiency using different solvents.
- To compare the extraction capabilities of acetone and methanol for fluoropolymers and individual per- and polyfluoroalkyl substances (PFAS).
Main Methods:
- Development of an in situ NMR tube extraction coupled with fluorine-19 (19F) NMR spectroscopy.
- Solid-liquid extraction of Viton A, Viton O-rings, and polytetrafluoroethylene in an NMR tube.
- Correlation of extraction efficiency with polymer swelling and permeation.
- Analysis of extracted fluorine composition using 19F diffusion-ordered spectroscopy NMR.
- Individual PFAS analysis using liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF).
Main Results:
- Acetone demonstrated a 2-fold greater permeation and higher extracted fluorine concentration compared to methanol.
- 19F NMR analysis indicated extracted fluorine originated from non-cross-linked Viton A.
- LC-QTOF confirmed increased extraction of perfluorooctanoic acid (PFOA) and perfluorohexanoic acid (PFHxA) over time and with swelling.
- No statistically significant difference in PFOA and PFHxA extraction between acetone and methanol was observed.
Conclusions:
- The developed in situ 19F NMR method offers a streamlined approach to quantify extracted fluorine, minimizing sample preparation.
- Polymer swelling significantly influences extraction efficiency, with acetone showing higher permeation.
- Nondiscriminatory fluorine measurements (e.g., by 19F NMR) require LC-QTOF confirmation for accurate individual PFAS identification.
- Methanol swelling is sufficient for extracting nonpolymeric molecules from Viton A, highlighting solvent-dependent extraction behavior.
