Stable Carbon Isotope Analysis of Perfluorooctanoic Acid (PFOA) by Microflow-High Pressure Liquid
Paul K Wojtal1,2, Brett Davidheiser-Kroll3, Chad S Lane1,2
1Center for Marine Science, University of North Carolina Wilmington, Wilmington, North Carolina, USA.
Rationale:
As contamination of perfluoroalkyl and polyfluoroalkyl substances (PFAS) in the environment becomes better understood, it is increasingly important to develop forensic tools capable of tracing contamination to emission sources. Isotopic methods have been previously inaccessible for PFAS due to limitations of the instrumentation, but high-pressure liquid chromatography (HPLC) coupled to Orbitrap mass spectrometry (Orbitrap MS) through electrospray ionization (ESI) allows measurement of the isotopic composition of individual PFAS compounds, such as perfluorooctanoic acid (PFOA).
Methods:
Six separate supplier-procured powders of PFOA were analyzed for their δ13C isotopic composition by microflow-HPLC-ESI-Orbitrap MS.
Results:
The method presented replicated, within error, the δ13C values measured using an elemental analyzer-isotope ratio mass spectrometer (EA-IRMS) for the six different supplier-procured PFOA powders. The offset from the EA-IRMS values for repeated analysis was between 0.2‰ and 1.1‰ and the error was between 0.8‰ and 1.5‰. Our Orbitrap-MS method requires approximately 0.04% of the material required to make an EA-IRMS measurement.
Conclusions:
We developed a method capable of measuring the carbon isotopic composition of PFOA, using HPLC-Orbitrap MS, with high precision and accuracy. This will allow future research to expand analytical capabilities for additional isotopologues of PFOA and other PFAS compounds.
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