Real-time measurements of gas phase per- and polyfluoroalkyl substances (PFAS) were performed in Central New Jersey air using chemical ionization mass spectrometry (CIMS). The CIMS was operated with Iodide as the reagent gas. Calibrations were performed for C₂ - C₆ perfluorinated carboxylic acids, and 4:2 and 6:2 fluorotelomer alcohols. Of these target analytes, only trifluoroacetic acid (TFA) was detected above instrumental detection limits in ambient air. Instrumental sensitivities were estimated for other detected PFAS including C₃H₂F₆O and C₆HF₁₁O₃. Mixing ratios of TFA reached up to 0.7 parts-per-trillion by volume (pptv). Estimated mixing ratios of C₃H₂F₆O and C₆HF₁₁O₃ reached the single pptv level. These latter two formulas are consistent with hexafluoroisopropanol (HFIP), & hexafluoropropylene oxide dimer acid (HFPO-DA) respectively, yet may represent multiple isomers. Diurnal profiles of detected PFAS, along with local meteorological data, may provide insight into potential local sources of these compounds. These results demonstrate the potential of online CIMS instrumentation for measuring certain PFAS in ambient air, in real time, at or below the pptv level. This approach also has potential for fenceline monitoring, and other near-source applications.

¹ U.S. Environmental Protection Agency, Research Triangle Park, NC

*Corresponding Author: offenberg.john@epa.gov