Due to the absence of an approved EPA method for PFAS analysis in matrices other than drinking water, many laboratories have developed in-house procedures for non-potable water and some solid matrices. The application of these procedures to more complex matrices like wastewater, sediments, biosolids, tissues and non-environmental matrices such as milk, serum, firefighting foam, and consumer products proves more challenging. From extraction to analysis, the presence of matrix interferences requires a variety of method modifications, particularly for longer lists of target PFAS. This presentation will address many of the considerations with various matrices and some of the techniques that can be employed to handle these challenges.
Per- and polyfluoroalkyl substances (PFAS) are a class of compounds that have been in use for decades but only within the last several years have gained public attention as chemicals of emerging concern (CEC). The stability of these compounds is advantageous in applications like aqueous film forming foams (AFFF), non-stick coatings and waterproof membranes, but are problematic in the environment as they are now known to be persistent and bioaccumulate. Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are the most studied compounds, however a multitude of other PFAS, along with their precursors, have expanded the list of PFAS that are analyzed by laboratories. Another challenging factor is ambient background contamination due to the prevalence of Teflon™ components in the lab environment. The USEPA is working on the development of methods to address non-potable water matrices, but for now, their drinking water methods EPA 537.1 and 533 are the only available published procedures. Consequently, laboratories have developed their own proprietary methods. The most common method modification is the use of isotope dilution quantitation which is critical for the analysis of non-drinking water matrices to account for the effects of matrix interferences on the data. However, many other challenges remain, such as how to handle large amounts of particulate in aqueous samples, foaming of samples during extraction, biphasic liquids, high organic content and particularly watery biosolids, and any type of AFFF or neat product. Fewer procedures exist compared to other organic methods for partitioning or sequestering interferences through cleanup techniques because of the varied physical and chemical characteristics of target PFAS. This presentation will cover these considerations in more detail and then provide some possible approaches for addressing these challenges along with questions to ask a contract laboratory to ascertain whether they have the tools and experience to handle complex matrices.
