Repeatability and Reproducibility of the Oasis™ WAX/GCB for PFAS Analysis Cartridges in Aqueous Samples for EPA Method 1633

In January 2024, EPA Method 1633 was finalized. EPA Method 1633 is the first method to incorporate the determination of 40 PFAS compounds across many challenging environmental sample matrices outside of drinking water, including non-potable waters (ground water, surface water, and wastewater) as well as soil, biosolids, and tissue by LC-MS/MS analysis. EPA Method 1633 requires use of both weak anion exchange (WAX) solid phase extraction with graphitized carbon black (GCB) cleanup and is a performance-based method allowing for modifications as long as acceptance criteria for recoveries and %RSDs are met.

This application note highlights the sample extraction for non-potable aqueous samples in EPA Method 1633 using a dual-phase, or bilayer cartridge: Oasis WAX/GCB for PFAS Analysis meeting the method acceptance criteria and displays reproducibility of the cartridges.

Benefits

• Oasis WAX/GCB for PFAS Analysis, a dual-phase cartridge is reproducible and repeatable for EPA Method 1633 aqueous samples in both inter- and intra-batch assays
• Reduction of manual steps, overall sample preparation time by use of the dual-phase SPE cartridge
• Acceptance criteria for recoveries and %RSDs are met for EPA Method 1633 for aqueous samples 

With EPA Method 1633 finalized, this introduces the first comprehensive US EPA method focused outside of drinking water for PFAS determination.¹ As the method incorporates a wide variety of matrices including ground water, surface water, wastewater, soil, biosolids, and tissue, their sample preparation to ensure reproducibility, sensitivity, and robustness is critical. In EPA Method 1633, the sample preparation incorporates two sorbents, WAX and GCB. For aqueous samples, extraction through a WAX cartridge is described first, followed by GCB clean up. However, the method is performance-based and gives requirements for establishing equivalency.¹ Oasis WAX/GCB for PFAS Analysis cartridges can alternatively be used and have been tested and shown to meet the acceptance criteria for multiple non-potable water sources as described previously.² Oasis WAX/GCB is a dual-phase, or bilayer cartridge which combines both sorbents into a single device benefitting the user by removing total manual steps in the sample preparation workflow and reducing time by up to 20% compared to use of loose GCB and a WAX cartridge. Additionally, Oasis WAX/GCB for PFAS Analysis undergoes a QC-batch release test for common PFAS to ensure cleanliness during the SPE process reducing the risk of false positives.

This application note uses Oasis WAX/GCB for PFAS Analysis on non-potable water samples showing that the acceptance criteria for EPA Method 1633 is met across three separate product lots of WAX/GCB with six replicates within each lot. This demonstrates the robustness of the SPE product in EPA 1633 workflows and the repeatability and reproducibility both inter- and intra-batch of WAX/GCB cartridges to ensure confidence in out-of-the-box performance of the cartridges lot after lot for use with complex matrices, like those in EPA Method 1633.

High repeatability both inter- and intra-batch from non-potable water samples using dual-phase Oasis WAX/GCB for PFAS Analysis cartridges. Recoveries and RSD% meet acceptance criteria of EPA Method 1633. 

This study demonstrates the reproducibility of the dual-phase Oasis WAX/GCB for PFAS Analysis cartridges for determination of 40 PFAS and standards using the ACQUITY UPLC I-Class System and Xevo TQ-XS Mass Spectrometer. The cartridges are suitable for PFAS analysis in accordance with EPA 1633 guidelines for recovery and %RSD. The WAX/GCB cartridges show excellent repeatability across multiple product lots and within multiple replicates of each lot across non-potable water samples. The data demonstrates Oasis WAX/GCB for PFAS Analysis cartridges are ideally suited for PFAS analysis from complex matrices, such as non-potable waters like those described in EPA Method 1633. Out of the box performance is expected lot to lot and within a lot for SPE when using Oasis WAX/GCB for PFAS Analysis.

1. US Environmental Protection Agency. Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Aqueous, Solid, Biosolids, and Tissue Samples by LC-MS/MS, Final version. 31 January 2024.
2. Organtini, K.; Rosnack, K.; Plummer, C.; Hancock, P.; Burt, O. Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Accordance With EPA 1633 Part 2: Analysis of Aqueous Matrices. Waters Application Note. 720008143. 2023.