In this article from Issue 13 of the Analytix Reporter, EPA Method 537.1 was used to demonstrate that the Millex® syringe filters with PES (polyethersulfone) Millipore Express® membranes did not give any detectable levels of PFAS contamination.
Guidelines and methods for measuring perfluoroalkyl substances (PFAS) in various matrices have been established by regulatory agencies in recent years. A key consideration for any PFAS method is to avoid contamination that can impact the accuracy of data, including those coming from sample preparation techniques such as filtration.
PFAS are poly- and perfluorylalkyl substances known as “forever chemicals” and comprise a group of over 4,000 varieties of long- and short-chain perfluorinated compounds. The excellent properties and broad use of PFAS, such as in firefighting foams and water-repellant clothing, has led to persistent accumulation of these man-made chemicals in environmental and biological matrices. These compounds have a potential negative impact on humans' health and aquatic life including liver damage, cancer, weakened immune system and high cholesterol.
In response, agencies in the US and Europe have taken regulatory action. The Stockholm Convention proposed regulations for two of the commonest PFAS compounds — perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) — with certain exemptions, effective in 2020.
Results and Discussion
PFAS extractables in nonsterile Millex® filters with PES membranes were measured according to EPA Method 537.1, with some additional PFAS compounds not required by the method including next-generation PFAS compounds (GenX). In all three lots that were tested for 0.22 µm and 0.45 µm syringe filters with PES membranes, no PFAS contaminants were detected even with the very low minimum detection limits (MDL) of the method. These results suggest that nonsterile Millex® syringe filters with PES membranes are reliable and appropriate for use in filtration of samples in the analysis of PFAS compounds in environmental matrices that require filtration prior to further clean-up, by solid phase extraction for example, and/or LC-MS/MS analysis.
Increasing concern about the threat of PFAS to human health has sparked a cascade of regulatory action in the US and Europe. While the primary focus has been on drinking water, other matrices containing higher particulates are also under investigation. Samples with higher particulates will require filtration prior to LC-MS/MS analysis or further SPE clean-up. Using EPA Method 537.1, no PFAS extractables were detected in nonsterile Millex® syringe filters with PES membranes. Therefore, when filtration of higher particulate samples is needed in a PFAS workflow, nonsterile Millex® syringe filters with PES membranes or nylon membranes (with or without glass fiber prefilter) are suitable options.