Abstract Per- and polyfluoroalkyl substances (PFAS) are recognized as persistent environmental contaminants, yet their regulatory definitions differ substantially. The U.S. Environmental Protection Agency (EPA) applies a narrow structural definition, whereas the Organization for Economic Co-operation and Development (OECD) adopts a broader framework encompassing millions of fluorinated species. This discrepancy directly affects which compounds are monitored and quantified, leaving many environmentally relevant fluorochemicals, such as trifluoroacetic acid (TFA), refrigerants, and other organofluorine (OF) compounds, unaccounted for. Compared to the OECD’s classification of PFAS, which can include up to 7 million species, the EPA definition only covers about 14,000 PFAS. Recent studies reveal that currently known PFAS explain only a small fraction of the total organofluorine (TOF) in environmental samples, underscoring the limitations of liquid chromatography with tandem mass spectrometry (LC-MS/MS) commonly used for targeted analysis. This review provides critical insights on other analytical methods that are underutilized for PFAS analysis, including combustion ion chromatography (CIC), fluorine-19 nuclear magnetic resonance spectroscopy ( 19 F-NMR), particle-induced gamma-ray emission (PIGE), and x-ray photoelectron spectroscopy (XPS), that can directly or indirectly measure fluorine. By highlighting their advantages and limitations, we propose how these tools can complement mass spectrometry to close the fluorine mass balance and improve monitoring of PFAS and related fluorochemicals. Finally, while solid-phase extraction (SPE) is a useful tool for matrix cleanup and analyte concentration, it is not appropriate for total fluorine determination because many compounds may be lost throughout the process. Alternatively, direct analysis and other extraction techniques are presented for better fluorine mass balance coverage. Graphical Abstract
Balasuriya et al. (2026) studied this question.