EPA Method 537 was recently expanded to EPA Method 537.1 in November 2018 to include four new per-/polyfluoroalkylsubstances (PFAS) compounds. While EPA Method 537.1 focuses on well-known PFAS, such as PFOA, PFOS, and GenX2, there are thousands of unknown PFAS that can potentially contaminate drinking water. Analysis of unknown contaminants requires high resolution and accurate mass capabilities in order to positively identify the molecular formula. This poster demonstrates that the quantitation of all PFAS outlined in EPA Method 537.1 can be performed on a quadrupole time-of-flight mass spectrometer (QTOF) at low parts per trillion concentrations in environmental drinking water samples. Quantitation limits on the QTOF are compared to a triple quadrupole mass spectrometer (QQQ).