Merit Laboratories offers several analytical options for PFAS. Analytical methods performed by Merit Laboratories include EPA 533, EPA 537 Rev. 1.1, EPA 537.1 ASTM D7979-19 with Isotopic Dilution, and ASTM D7968-17. The following summary will help guide you through selecting the most appropriate PFAS method for your project. EPA 537 Rev. 1.1: This is a drinking water method for 14 PFAS compounds using Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS).