Advancing Total Fluorine Measurement of PFAS in Liquid Samples Using HR-CS-GFMAS

Per- and polyfluoroalkyl substance (PFAS) analysis with liquid chromatography-mass spectrometry (LC-MS) is time-consuming and costly in estimating total PFAS. A quick and lower-cost approach for estimating PFAS-derived total fluorine as a total PFAS proxy for sample prioritization is needed. Total fluorine methods for liquid samples using high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) exhibited unsatisfactory fluorine recovery in previous work, and a high limit of quantification (LOQ = 5.13 μg/L), and required a perfluorooctanoic acid (PFOA) reinjection step for each sample. Herein, we: 1) clarified the role and optimized the modifier prepretreatment composition and delivery; 2) identified optimal pyrolysis and atomization temperatures; 3) improved the background correction approach; and 4) validated fluorine recovery for 48 PFAS. Fluorine recoveries of the optimized method were compared to the literature and applied to two environmental samples. The final method exhibited an LOQ of 1.1 μg/L as F– and fluorine recoveries of 70–110% for most PFAS (average 90.3%) spanning 8 structural PFAS groupings. Moreover, the method demonstrated high reproducibility and consistent recovery across a broad PFAS concentration range and in the two environmental samples. The optimized HR-CS-GFMAS method is rapid, and cost-efficient and achieves high precision and accuracy for total PFAS fluorine.