Perfluoroalkyl Substances (PFAS) Testing Guide

Importance of the Topic

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are persistent environmental pollutants found widely in drinking water. Due to their resistance to degradation and potential health impacts including cancer, endocrine disruption and immune effects, accurate and sensitive measurement of PFAS at ng/L levels is essential for public health, regulatory compliance and environmental monitoring.

Objectives and Overview

This guide summarizes key analytical approaches for PFAS testing in drinking water. It reviews the official US EPA methods 537.1 and 533, outlines a large-volume direct injection technique, and describes available certified reference materials. The aim is to illustrate method performance, instrumentation requirements and best practices for high throughput PFAS analysis.

Methodology and Instrumentation

– EPA Method 537.1 employs styrene-divinylbenzene (SDVB) solid phase extraction (Strata SDB-L cartridges) followed by UHPLC separation on a 1.6 µm PS C18 Luna Omega column and MS/MS detection (Agilent Ultivo or equivalent). Sample volumes of 250 mL are fortified with isotopic surrogates, eluted with methanol, dried and reconstituted before a 10 µL injection.

– EPA Method 533 uses weak anion-exchange SPE (Strata-X-AW cartridges) and isotope dilution for 25 PFAS analytes, including short-chain and replacement compounds. The extract is eluted with ammonia in methanol, dried, reconstituted and analyzed on a 3 µm Gemini C18 column with ESI-MS/MS.

– A large-volume direct injection approach dilutes 1 mL water sample with 0.65 mL methanol, adds surrogates and injects 950 µL directly onto a 100 × 3.0 mm Gemini C18 column. This method reduces sample prep steps and achieves ng/L detection limits.

Key Results and Discussion

All methods demonstrated excellent linearity (R2 > 0.99), recoveries of 90–115 % and precision < 15 % RSD across target PFAS. Method 537.1 achieved run times under 9 min, a three-fold reduction versus the original 25 min protocol. Method 533 delivered robust quantitation for 25 analytes including GenX, with accuracy within ± 10 % at low ng/L levels. Direct injection maintained detection limits near 1 ng/L, with minimal blank carryover using a delay column and instrument upgrades.

Benefits and Practical Applications

• Regulatory compliance: fully compatible with EPA 537.1 and upcoming UCMR5.
• High throughput: shortened run times and reduced prep maximize laboratory productivity.
• Flexibility: choice of SPE or direct injection tailored to sample load and instrument configuration.
• Comprehensive scope: inclusion of legacy PFOS/PFOA and emerging short-chain and ether PFAS.

Future Trends and Applications

Advances will focus on expanded analyte lists, including novel PFAS chemistries, further reduction of detection limits via large-volume injection and on-line SPE, improved column chemistries to resolve branched isomers, and integration of certified reference materials to ensure data quality. Automation and miniaturization will support routine monitoring as regulatory standards evolve.

Conclusion

Robust LC-MS/MS methods—EPA 537.1 SPE-LC, EPA 533 WAX-SPE with isotope dilution, and large-volume direct injection—provide sensitive, accurate and rapid PFAS testing in drinking water. Adoption of optimized SPE sorbents, UHPLC columns and isotopic standards ensures reliable quantitation to support environmental laboratories and water utilities in meeting stringent health advisory limits.

Reference

• US EPA Method 537.1: LC-MS/MS determination of PFAS in drinking water.
• US EPA Method 533: Isotope dilution anion-exchange SPE and LC-MS/MS for PFAS.
• Buck et al., Integr. Environ. Assess. Manag. 2011, 7(4), 513–541.
• ISO 25101:2009 – Water quality: PFOS/PFOA determination by SPE and LC-MS.