Spatial and Temporal Analysis of Fluorine Mass Balance in Swedish Sludge and the Impact of Sample Treatment on Extractable Organofluorine.

Per- and polyfluoroalkyl substances (PFAS) are an extensive group of anthropogenic compounds with a large diversity of classes. Relying only on target analysis may underestimate the level of PFAS contamination in the environment. The extractable organofluorine (EOF) mass balance is a widely applied method to estimate the fraction of organofluorine not captured by target analysis. This study aimed to conduct a comprehensive EOF mass balance analysis on sludge and evaluate the impact of three different sample treatments on target PFAS and EOF, as well as their respective mass balance. Two complementary sample treatments were applied to 26 Swedish sludge samples: ion-pair extraction (IPE) for anionic and neutral PFAS, and hexane:acetone extraction (Hx:Ac) for nonpolar PFAS. The results demonstrated that the EOF concentrations were highly influenced by the sample treatment. The IPE method observed up to 40 times higher EOF concentrations than the Hx:Ac method, indicating a high proportion of polar organofluorine. Unidentified EOF increased between 2004 and 2017 for both sample treatments. These findings demonstrate that both polar and nonpolar organofluorine contribute to the EOF and that no single method captures them. In the present study, only two side-chain fluorinated copolymers were monitored, and other fluorinated polymers may be contributors to the unknown EOF.