Evaluation of iodide chemical ionization mass spectrometry for gas and aerosol-phase per- and polyfluoroalkyl substances (PFAS) analysis

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

Real-time measurements of short-chain (C < 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.Implications: 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 < 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.

Characterizing Volatile Emissions and Combustion Byproducts from Aqueous Film-Forming Foams Using Online Chemical Ionization Mass Spectrometry

Aqueous film-forming foams (AFFFs) are used in firefighting applications and often contain per- and polyfluoroalkyl substances (PFAS), which can detrimentally impact environmental and biological health. Incineration is a potential disposal method for AFFFs, which may produce secondary PFAS and other air pollutants. We used online chemical ionization mass spectrometry (CIMS) to measure volatile PFAS emissions from incinerating AFFF concentrate solutions. We quantified perfluorinated carboxylic acids (PFCAs) during the incineration of legacy and contemporary AFFFs. These included trifluoroacetic acid, which reached mg m-3 quantities in the incinerator exhaust. These PFCAs likely arose as products of incomplete combustion of AFFF fluorosurfactants with lower peak furnace temperatures yielding higher PFCA concentrations. We also detected other short-chain PFAS, and other novel chemical products in AFFF combustion emissions. The volatile headspace above AFFF solutions contained larger (C ≥ 8), less oxidized PFAS detected by CIMS. We identified neutral PFAS resembling fluorotelomer surfactants (e.g., fluorotelomer sulfonamide alkylbetaines and fluorotelomer thioether amido sulfonates) and fluorotelomer alcohols in contemporary AFFF headspaces. Directly comparing the distinct chemical spaces of AFFF volatile headspace and combustion byproducts as measured by CIMS provides insight toward the chemistry of PFAS during thermal treatment of AFFFs.

Avoiding Regrettable Replacements: Can the Introduction of Novel Functional Groups Move PFAS from Recalcitrant to Reactive?

Per- and polyfluoroalkyl substances (PFASs) are present in a range of commercial and consumer products. These chemicals are often high-performance surfactants or nonstick/water-repellant coatings due to their chemical stability; however, this stability leads to select PFAS being environmentally persistent. To facilitate degradation, new fluorosurfactant building blocks (F7C3-O-CHF-CF2-S-CH2-CH2-OH (FESOH), F3C-O-CHF-CF2-S-CH2-CH2-OH (MeFESOH), F7C3-O-CHF-CF2-O-CH2-CH2-OH (ProFdiEOH), F7C3-O-CHF-CF2-CH2-OH (ProFEOH), and F3C-O-CHF-CF2-O-CH2-CH2-OH (MeFdiEOH)) have been systematically developed with heteroatom linkages such as ethers, thioethers, and polyfluorinated carbons. The room temperature, gas-phase OH oxidation rate constants, and products of these chemicals were monitored in an atmospheric chamber to investigate their fate in the atmosphere. Analysis was performed using online high-resolution chemical ionization mass spectrometry (CIMS) using the iodide reagent ion and via offline UPLC-MS/MS. FESOH and MeFESOH, the thioether congeners, were observed to have the largest rate constants of kFESOH = 2.82 (±0.33) and kMeFESOH = 2.17 (±0.17) (×10-12 cm3 molecules-1 s-1, respectively). First-, second-, and third-generation products of OH oxidation were observed as a function of time, while product quantification yielded ultrashort perfluoropropionic acid (PFPrA) and short polyfluoroether acid species as the terminal products for FESOH and ProFdiEOH. There was evidence for MeFESOH being fully mineralized, demonstrating the potential benign chemical architecture.

Cloth-Air Partitioning of Neutral Per- and Polyfluoroalkyl Substances (PFAS) in North Carolina Homes during the Indoor PFAS Assessment (IPA) Campaign

Partitioning of per- and polyfluoroalkyl substances (PFAS) to indoor materials, including clothing, may prolong the residence time of PFAS indoors and contribute to exposure. During the Indoor PFAS Assessment (IPA) Campaign, we measured concentrations of nine neutral PFAS in air and cotton cloth in 11 homes in North Carolina, for up to 9 months. Fluorotelomer alcohols (i.e., 6:2 FTOH, 8:2 FTOH, and 10:2 FTOH) are the dominant target species in indoor air, with concentrations ranging from 1.8 to 49 ng m-3, 1.2 to 53 ng m-3, and 0.21 to 5.7 ng m-3, respectively. In cloth, perfluorooctane sulfonamidoethanols (i.e., MeFOSE and EtFOSE) accumulated most significantly over time, reaching concentrations of up to 0.26 ng cm-2 and 0.24 ng cm-2, respectively. From paired measurements of neutral PFAS in air and suspended cloth, we derived cloth-air partition coefficients (Kca) for 6:2, 8:2, and 10:2 FTOH; ethylperfluorooctane sulfonamide (EtFOSA); MeFOSE; and EtFOSE. Mean log(Kca) values range from 4.7 to 6.6 and are positively correlated with the octanol-air partition coefficient. We investigated the effect of the cloth storage method on PFAS accumulation and the influence of home characteristics on air concentrations. Temperature had the overall greatest effect. This study provides valuable insights into PFAS distribution, fate, and exposure indoors.