Development of a U.S. EPA drinking water method for the analysis of selected perfluoroalkyl acids by solid-phase extraction and LC-MS-MS.

A drinking water method for perfluoroalkyl acids (PFAAs) is presented that addresses the occurrence monitoring needs of the U.S. Environmental Protection Agency (EPA) for a future unregulated contaminant monitoring regulation (UCMR). This paper describes the challenges associated with developing an analytical method for 14 PFAAs that will be used for drinking water occurrence monitoring. The method employs solid-phase extraction with analysis by liquid chromatography-tandem mass spectrometry (LC-MS-MS). The final method preservation scheme requires that samples be stored in polypropylene bottles and that they be buffered and free chlorine removed with Trizma buffer. Mean recoveries of chlorinated surface water samples fortified with the PFAAs at 40-100 ng/L (except for the perfluorooctane-sulfonamido-acetic acids at 200 ng/L) are 85-112% with < 5% relative standard deviation. Single laboratory minimum reporting limits of 2.9-14 ng/L are demonstrated with this methodology. The final method meets all of the EPA UCMR survey requirements for sample collection and storage, precision, accuracy, and sensitivity and is expected to be proposed for use under a future UCMR.