LAUSR

In this study, we measured the effects of sample type and storage temperature on the stability of 29 per- and polyfluorinated alkyl substances (PFAS) in water. Spiked bottled water, surface water, and two types of effluent samples were stored in HDPE containers at +20⁰C, 4⁰C, and -20⁰C over a period of up to 180 days. The analytes studied included: C4 through C14 perfluorinated carboxylates (PFCA), C4 through C10 and C12 perfluorinated sulfonates (PFSA), 4:2, 6:2 and 8:2 fluorotelomer sulfonates (FTS), three perfluorooctane sulfonamides (PFOSA, N-MeFOSA, N-EtFOSA), two perfluorooctane sulfonamide ethanols (N-MeFOSE and N-EtFOSE), and two perfluorooctane sulfonamideacetic acids (N-MeFOSAA and EtFOSAA). Overall, ten analytes; PFOA, PFNA, 8:2 FTS, PFOSA, N-MeFOSA, NEtFOSA, N-MeFOSAA, N-EtFOSAA, N-MeFOSE, and N-EtFOSE showed increasing or decreasing concentration trends under at least one of the experimental conditions investigated. Increases in concentrations of N-MeFOSAA and N-EtFOSAA in surface water and effluent samples at +20⁰C, and 4⁰C correlated with the decreases in the concentrations of N-MeFOSE and N-EtFOSE respectively, suggesting analyte interconversion during sample storage. This is the first time such analyte conversion is reported in samples under storage and demonstrates the importance of assessing stability of PFAS in environmentally relevant matrices. The significance of this study extends beyond sample storage for analysis, as toxicological and exposure studies conducted at room temperature also need to consider the significance of analyte degradation through the exposure process.