Automating Sample Prep for EPA Method 533 – Analysis of PFAS in Drinking Water Using LC-MS/MS

[chris-shevlin]

Per- and polyfluoroalkyl substances (PFAS) contamination is still a growing area of concern in all areas of the environment. The presence of these substances in drinking water is one of the most important and impactful, regarding healthy and safe water. In December of 2019, the US EPA released a new validated method for PFAS testing in drinking water, Method 533. This method expands the target list by 11 compounds which are the “short-chain” substances, or those which have carbon chain lengths from four to twelve. US EPA Method 533 also incorporates isotope dilution to reduce matrix interference and improve data. The addition of the “short-chain” molecules is important because these are suspected to be some of the most soluble in water and have high mobility in soil.

EPA 533 requires samples are prepared with solid-phase extraction (SPE) with a weak-anion exchange (WAX) sorbent, prior to LC-MS/MS analysis. WAX is an excellent sorbent material because the short-chain PFAS tend to be more polar due to the shorter carbon chain length and many of these compounds are sulfonic acids or other types of organic acids.

SPE is known to be a very good method for sample prep, but it is very labor-intensive, time-consuming and can be prone to errors because of all the manual steps involved. Due to SPE needing so much manual interaction, there are many points in the process where background PFAS contamination can be introduced into the sample. PFAS can be found in so many common and laboratory items, it is not reasonably achievable to completely eliminate from the lab environment.

Adding automation to the SPE portion of EPA 533 is key to improving the data quality, keeping background to a minimum and greatly improving laboratory efficiency. When US EPA method 533 sample preparation was done using the Thermo Scientific ™ Dionex ™ AutoTrace 280 PFAS automated Solid-phase Extraction instrument, all of these benefits were observed. Automation gives excellent data quality and very precise control over the flow rates at critical steps. Loading or eluting too quickly can cause loss of analytes resulting in poor recoveries and reproducibility or even false negatives. Since the AutoTrace 280 PFAS uses non-fluoropolymer materials and does not require constant interaction, background is well below method requirements.

The other benefit to using automation is the elimination of constant attention to the process. In a very short period, the instrument is set up and run with the push of a few buttons, no software needs to be learned to run samples on the AutoTrace 280 PFAS. This allows you to now accomplish other tasks while your samples are being prepared. Even those who have never run SPE can do this step of the method with ease.

To learn more, download our U.S. EPA Method 533: Determination of Per- and Polyfluorinated Alkyl Substances (PFAS) in Drinking Water Using Automated Solid Phase Extraction and LC-MS/MS