Assessing PFAS total in landfill leachate through multiple extraction methods and fluorine mass balance

Comprehensive quantification of per- and polyfluoroalkyl substances (PFAS) and extractable organofluorine (EOF) for assessing PFAS total in complex environmental matrices requires extraction methods capable of retaining chemically diverse fluorinated compounds. In this study, the performance of three solid-phase extraction (SPE) sorbents (weak anion exchange (WAX), weak cation exchange (WCX), and hydrophilic-lipophilic balance (HLB)) was comprehensively evaluated for the extraction of selected targeted PFAS and inorganic anions and determination of extractable fluorine from landfill leachate. Recovery experiments covering multiple PFAS classes, including PFCA, PFSA, zwitterionic PFAS, and bis-FASI, together with inorganic fluorinated anions, showed clear sorbent-dependent selectivity. WAX provided the most consistent recoveries across compound classes and yielded comparable concentrations of Σ₃₃PFAS + BF₄^- and EOF, indicating retention of a broad fraction of fluorinated compounds and a closed fluorine mass balance. In contrast, WCX resulted in lower EOF concentration and a negative fluorine mass balance, attributed to matrix composition that emerged as a critical factor controlling EOF recovery, with divalent cations (Ca²⁺ and Mg²⁺) causing significant EOF suppression. HLB also yielded lower EOF concentrations, primarily due to poor retention of ultra-short-chain PFAS that contributed significantly to the overall fluorine balance, and similar behavior was observed for WCX. In addition, retention of inorganic fluorinated anions indicates that EOF concentrations included both organic and inorganic fluorinated compounds. The findings reveal that both sorbent chemistry and matrix chemistry critically influence EOF quantification, thereby affecting fluorine mass balance.