In what many scientists believe will be a significant advancement in analytical testing methodology, ASTM is planning to release a new Standard Test Method for PFAS in aqueous sample matrices. This new method, ASTMD8421-21, utilizes Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS) with Isotope Dilution (ID). It is anticipated to be the first published ASTM method for PFAS that incorporates isotope dilution in the actual method and not simply a footnote.