Single-Injection Screening and Quantitation of Gen-X and 24 Other PFASs in Water and Soil Using Various Tandem Mass Spectrometry Workflows

Characterization of Polyfluoroalkyl Substances in the Environment
Oral Presentation

Prepared by O. Cabrices, P. Winkler, S. Roberts, C. Butt
SCIEX, 500 Old Connecticut Path, Framingham, MA, 010701, United States


Contact Information: [email protected]; 908-472-4797


ABSTRACT

Due to the environmental persistence of PFOA, PFOS, and other similar compounds, industrial and commercial fluorochemical manufacturers have started producing alternatives. These alternatives have been identified as ether forms of PFOA and other similar compounds. One of these new compounds is referred to as Gen-x, with the chemical name HFPO-DA. This compound has been detected in the environment at multiple contaminated sites and has been added to the EPA 537.1 method. It is important for any PFAS testing lab to include these compounds in their protocols.

In this study, different LC/MS/MS workflows to detect and quantitate HFPO-DA, DONA, and ADONA, in water and soil samples were evaluated. The use of a Scheduled MRM algorithm using the SCIEX 5500 QTRAP system that automatically triggers secondary MRM transitions, for increased data quality and confidence in analyte detection at low ng/mL concentration levels is described; as well as the use of a quantitative High Resolution MRM workflow using the SCIEX X500R QTOF system to provide high-resolution, accurate-mass data for full-scan information of both precursor ion and all product ions.

The methodology presented also includes 24 other commonly tested PFAS using two different sample preparation methods: The first was a dilute-and-shoot method that used an optimized methanol content of 40% to maintain all of the PFAS compounds in solution while maintaining HPLC peak shape. The second method utilized solid phase extraction (SPE) with ion exchange, mixed mode cartridges, and further cleanup using graphitized carbon. Analytes were chromatographically separated using a Phenomenex Gemini C18 column. Mobile Phase was ammonium acetate in water and in methanol, 600 ÁL/min flow rate. The LC/MS-MS Systems were operated in negative electrospray mode. Samples were evaluated against a list of parameters containing the names, molecular weights and retention times for all compounds.

The retention time determined by the optimized LC conditions combined with high-resolution mass spectrometry and MS/MS spectra, enabled accurate compound identification across the workflow. On the other hand the sensitivity of the QTRAP System allowed the SPE extract to be injected directly without concentration using nitrogen, which improved recovery of several PFAS classes, including FOSAs.