Comparison of Real-Time and Offline Mass Spectrometry Methods for Quantitation of Fluorotelomer Alcohols in Aqueous Film-Forming Foam Headspace

Per- and polyfluoroalkyl substances (PFAS) are highly water-, grease-, and heat-resistant compounds known as "forever chemicals" due to their resistance to degradation. Aqueous film-forming foams (AFFFs) are PFAS-containing firefighting foams and a known source of environmental PFAS contamination. Recent research characterizing PFAS contamination at historical AFFF usage sites has advanced our understanding of environmental fate and transport of water-soluble PFAS. However, emissions of volatile or semivolatile PFAS from AFFFs during their storage and application and from AFFF-contaminated sites remain largely uncharacterized, in part due to analytical method limitations. This work quantified fluorotelomer alcohols (FTOHs) in the headspace above three AFFF formulations using two emerging analytical techniques: thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) and real-time iodide chemical ionization mass spectrometry (I-CIMS). Thermal desorption tube samples were collected for offline analysis via TD-GC/MS, while I-CIMS simultaneously sampled the headspace. Then, the FTOH headspace concentrations quantified by the two techniques were compared. In all three formulations, 6:2 and 8:2 FTOHs were the most and second-most abundant, respectively. The FTOH concentrations quantified by TD-GC/MS ranged from 0.06 to 2.0 μg/m³, while those quantified by I-CIMS ranged from 0.13 to 4.4 μg/m³. The percent error between the two methods ranged from 10 to 102%. These results underscore the need for additional research exploring the factors that impact the quantitative accuracy of both methods.