Dynamic headspace extraction as an alternative method to collect PFAS from environmental samples

Per- and polyfluoroalkyl substances (PFASs) are a family of fluorinated compounds extensively used since 50s by both consumers and industry. Structurally, they consist of a carbon chain bonded to fluorine atoms, with varying functional groups at the end of the chain. Due to their environmental persistence and potential adverse health effects, developing robust analytical methodologies for PFAS is crucial. In this context, thermal desorption tubes, combined with gas chromatography, provide a solvent-free extraction method and high analytical performance alternative to the analysis of PFASs. Therefore, the aim of this research is to evaluate the capabilities of thermal desorption tubes as extraction method, coupled with GC and GC×GCTOFMS, to characterize (semi)volatile PFAS. In order to assess the thermal desorption tubes performance, different sorbents (graphitized carbon black and phenylphenilen oxide polimers) and extraction parameters (conditioning temperature and extraction volume) were evaluated in terms of recovery and selectivity for PFAS extraction. The extraction was optimized using environmental samples (soil and water) spiked with a mix of PFAS standards (MW range 264-571 Da), including fluorotelomer alcohols (FTOH), acrylates (FTAc), and alkyl sulfonamide (N-MeFOSA, N-EtFOSA, N-MeFOSE, and N-EtFOSE) derivatives. For this purpose, both GC and GC×GC, coupled with TOFMS, were used. The porous polymer poly(2,6-diphenylphenylene oxide) was the most effective sorbent, although graphitized carbon adsorbent also proved useful for extracting certain compounds. The use of GC×GC revealed additional significant molecules in environmental samples, and TOFMS demonstrated its analytical power in distinguishing individual PFAS, even within the same subfamily. These preliminary tests were essential for understanding the behaviour of these PFAS’s families both as standards and in real samples. The thermal desorption tubes have demonstrated to be a valid choice to extract these chemical molecules, minimizing solvents usage. When combined with GC(×GC)-TOFMS, this method represents a new alternative to traditional extraction.