A Method to Measure Total Gaseous Fluorine

Abstract

Total fluorine (TF) analysis is a powerful tool for the characterization of organofluorine contaminants in the environment. Organofluorine compounds are known primarily with respect to the notorious poly- and perfluoroalkyl substances (PFAS) and as potent greenhouse gases that can impact the climate. The use of targeted methods for every organofluorine compound in the environment is not feasible. While methods are available for TF analysis of condensed phase samples, no technique exists for gas phase TF measurements (TF_g). Herein we demonstrate an in situ instrumental method for TF_g via platinum catalyzed thermolysis at 1000 °C in the presence of propane. TF_g is fully converted into HF and subsequently quantified by an ion selective electrode or ion chromatography for F^–. The method was validated using nine organofluorine compounds with differing functional groups. We characterized TF_g and compared it to common speciated measurements in the headspace of four commercial fluorosurfactants and outdoor air. Most TF_g (65.0–99.8% or 1.5–10.2 ppmv F) in the fluorosurfactant headspace was unknown. In outdoor air, >50% of TF_g (7.2–24.2 ppmv F) was unknown. These high quantities of unknown organofluorine indicate a measurement gap in the gas phase, which could have important implications for atmospheric sources and the burdens of PFAS and fluorinated greenhouse gases.