Direct and Offline Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Ground, Surface and Waste Water by LC-MS/MS

Characterization of Polyfluoroalkyl Substances in the Environment
Oral Presentation

Prepared by , C. Jacob, C. Martins

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Per- and polyfluoroalkyl substances (PFAS) have been manufactured and used in a variety of industries around the globe, including in the United States since the 1940s. PFOA and PFOS have been the most extensively produced and studied of these chemicals. Both chemicals are very persistent in the environment and in the human body and accumulate over time. There is evidence that exposure to PFAS can lead to adverse human health effects.1-3As a result, analytical testing has expanded beyond the simple analysis of drinking water, and is now being performed on several matrices such as ground, surface and wastewater. In this work, we report a direct analysis method for the determination of a list of 24 PFAS in a wide variety of non-drinking matrices. The LC-MS/MS system comprised a Thermo Fisher Vanquish™ Flex Binary UHPLC System fitted with PFC free kit and interfaced with a Thermo Fisher TSQ Altis™ Triple Quadrupole Mass Spectrometer equipped with and H-ESI ionization probe which was used in negative ionization mode. The cycle time for the negative SRM transitions was 0.3 s. Water samples were provided by the U.S. EPA Region 5, and were 2-fold diluted in methanol, filtrated, and acidified prior LC-MS/MS analysis. The LC-MS/MS method described herein differs from the reported ASTM 9797-17 and EPA 8327 methods, where excellent chromatographic separation was achieved on a Thermo Accucore RP-MS analytical column using different mobile phases compositions. Good linearity and quantitative accuracy were achieved over the range of 5-200 ng/L, with correlation coefficients greater than 0.99 for all transitions and the respective residuals were within 20% of the nominal values. LLOQ values of 2 ng/L were achieved for certain PFAS compounds, which is 5 times lower than the LLOQ reported by ASTM 9797-17 and EPA 8327, thus demonstrating the high sensitivity of TSQ Altis mass spectrometer for the quantitation of PFAS at very low levels. PFAS compounds were detected in the different water matrices at both low and high spike concentrations with recoveries within the range required by ASTM D7979-17 and EPA 8327 methods. All spiked non-drinking water samples, in a variety of matrices, showed RSDs below 20% for most of the PFAS compounds demonstrating the high robustness and reproducibility of the method. We will also show the results for a new, PEEK free system for Offline SPE.