Per- and polyfluoroalkyl substances (PFAS) are emerging anthropogenic pollutants with some or all the hydrogen atoms exchanged with fluorine. Recent studies demonstrate that single ppt levels of PFAS in environmental media can lead to a variety of known adverse health effects. Considerable amounts of various PFAS compounds are present in the gas phase due to their higher vapor pressure than their analogous hydrocarbons, making inhalation a potential important exposure pathway. However, real-time detection of gas-phase PFAS is challenging and limited due to their relatively low atmospheric concentrations. This study presents the first online method to detect and quantify hydrofluoro olefin and hydrofluoroalkane species, which are considered PFAS, using CIMS. Selected types of fluoro-olefins, fluoro-alkanes, and vinyl ethers, including 2,3,3,3-tetrafluoropropene (HFO-1234yf) and 1,1,1,2,3-pentafluoropropane (HFC-245eb), are detected and calibrated using the NO⁺ reagent ion, through reagent adduct (R-NO⁺), hydride abstraction (R–H^-), or charge transfer (R⁺). Compared with the proton-transfer-reaction (PTR) mode, the sensitivity of HFO, a new refrigerant, and HF-alkane in the NO⁺ mode has been increased by up to 10³ orders of magnitude with detection limits reaching 8.8 ppt and 205 ppt, respectively. In addition, the detection limits of perfluoroalkenes (PFOs) and fluorotelomer acrylates in NO⁺ mode are also in the ppt levels. Mobile field measurments using the Texas A&M Mobile Laboratory were conducted at a PFAS manufacture plant, showing real-time detection of HFO in the atmosphere. The application of the NO⁺ mode to characterize and quantify PFAS species provided an essential and unique real-time methodology for examining PFAS in the positive ion mode, especially for emerging PFAS compounds with low to zero sensitivities in the PTR or iodide ionization modes.

Gabrielle West

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