Measuring short-chain per- and polyfluoroalkyl substances in Central New Jersey air using chemical ionization mass spectrometry

Real-time measurements of short-chain (C &lt; 8) per- and polyfluoroalkyl substances (PFAS) were performed in Central New Jersey air using chemical ionization mass spectrometry (CIMS). The CIMS was calibrated for C₂ – C₆ perfluorinated carboxylic acids, and 4:2 and 6:2 fluorotelomer alcohols. Of these, only trifluoroacetic acid (TFA) was detected in ambient air above instrumental detection limits. However, instrumental sensitivities (and thus ambient mixing ratios) were estimated for other detected PFAS including C₃H₂F₆O and C₆HF₁₁O₃. TFA mixing ratios reached up to 0.7 parts-per-trillion by volume (pptv). Estimated C₃H₂F₆O and C₆HF₁₁O₃ mixing ratios reached the single pptv level. These latter two formulas are consistent with hexafluoroisopropanol (HFIP) and hexafluoropropylene oxide dimer acid (HFPO-DA) respectively, though they may potentially represent multiple isomers. Diel profiles of detected PFAS, along with local meteorological data can provide information on potential local sources of these compounds. However, only limited discussion of potential sources was provided here given the sparse detection of these compounds above instrument detection limits. These results demonstrate the potential of online CIMS instrumentation for measuring certain PFAS in ambient outdoor air in real time at or below the pptv level. This technique also has potential for fenceline monitoring and other near-source applications. <i>Implications</i>: Online chemical ionization mass spectrometry (CIMS) has potential for fast, real-time measurements of certain airborne per- and polyfluoroalkyl substances (PFAS). Three short-chain (C &lt; 8) PFAS were detected by CIMS in Central New Jersey ambient air near or above the parts-per-trillion by volume (pptv) level. This technique also has potential for fenceline monitoring and other near-source applications for airborne PFAS.