Perfluorinated Alkyl Substances (PFAS) are a group of anthropogenic chemicals widely used as fire retardants or non-stick coatings but there are concerns about their potent hazadous effects. To safeguard public health to these chemicals, the US, EU and Australia have issued health advisory guidelines for perfluorooctanoic acid (PFOA) and perfluorooctane-sulfonic acid (PFOS) in drinking water. US Environmental Protection Agency has established Method 537 for PFAS in drinking water. It utilizes a solid phase extraction followed by LC-MS/MS for the determination of 14 PFAS. Here we expanded the targets to 21 PFAS using LCMS-8050 and LCMS-8045.