Exploiting GC(×GC)-HRMS capabilities for targeted and non-targeted analysis of (semi)volatile poly- & perfluorinated hydrocarbons in ambient air

Introduction Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are a family of manufactured chemicals that are widely employed in consumer goods and industrial applications because of their special qualities. Chemically, these compounds contain a chain of carbon atoms bonded to multiple fluorine atoms, and with different functional groups at the end of the chain. A portion of these chemicals exhibit a neutral and volatile nature, and are recently gaining more attention from environmental agencies, since they can be released by consumer goods and detected in the air. Even at molecular weights over 600 Da, the presence of fluorine atoms in PFAS makes them more volatile than non-fluorinated analogues, due to weak van der Waals interaction properties. Therefore, they are suitable for GC-MS analysis. Methods In the current research, a parallel GC and GC×GC methodology coupled with both low-resolution and high-resolution TOF-MS was developed for the (semi)volatile PFAS analysis. Specifically, the chemical group under study were fluorotelomer alcohols (FTOH), acrylates (FTAc), and alkyl sulfonamide (N-MeFOSA, N-EtFOSA, N-MeFOSE, and N-EtFOSE) derivatives. Regarding the MS ion source, both electron impact, positive chemical ionization, and negative chemical ionization were exploited to study the spectra of the targeted chemical groups. Dynamic headspace extraction was used for air sampling, using the most appropriate adsorbent material in terms of selectivity and sensitivity. Initially, the extraction method was optimized in terms of sampling volume and adsorbent type using a mix of PFAS standards (MW range 264-571 Da) and different spiked household goods. Preliminary data – Limit 300 words The initial method optimization and evaluation of the standard mixture provided satisfactory mass accuracies for the target analytes, ranging from -0.06 to +2.7 ppm for m/z 462.998521 ([M-H] + ) and 511.960756 ([M-CH3] + ), respectively. The use of multiple ionization forms combined with HRMS allowed for high-level information of the target compounds, allowing both fragments fingerprinting and molecular ion presence, useful for the generation of a dedicated mass spectral library and for the identification of unknown congeners or homologues series. In terms of sensitivity, the instrumental LOD reached sub ppb levels. The developed approach, including the dynamic headspace extraction, the GC(×GC) separation, and the HRMS combines high-sensitivity and high-resolution for both confirmatory and exploratory analysis of known and unknown PFAS in ambient air. Indeed, dynamic sampling allows for high-reconcentration factors, the GC allows for the separation of structural isomers, and the HRMS allows for the confirmation of known PFAS and annotation of unknown homologs. Novel aspect – Limit 20 words The growing concerns regarding the (semi)volatile PFAS make the approach and research insights highly relevant for their characterization and determination.