Handbook of Analysis Procedures for EPA method 537.1

Importance of the Topic

The analysis of per- and polyfluorinated alkyl substances (PFAS) in drinking water is critical for public health and environmental safety. These persistent compounds can accumulate in human tissues and ecosystems, prompting stringent regulatory limits. Method 537.1 offers a robust workflow to detect trace levels of 18 PFAS compounds using solid-phase extraction (SPE) coupled to liquid chromatography/tandem mass spectrometry (LC-MS/MS).

Study Objectives and Overview

This handbook describes a two-stage approach: an Initial Demonstration of Capability (IDC) followed by routine Sample Analysis. IDC establishes method performance in a laboratory setting, including Minimum Reporting Levels (MRLs), calibration curves, system background checks, and quality control (QC) criteria. Once validated, the method is applied to field samples with ongoing QC checks to ensure data reliability.

Methodology and Instrumentation

The workflow begins with the preparation of standard solutions: analyte primary dilution standards, internal standards, and surrogate standards at concentrations tailored for 10 µL fortifications. QC samples include laboratory reagent blanks (LRB), laboratory fortified blanks (LFB), fortified sample matrices (LFSM), and duplicates. SPE cartridges are conditioned with methanol and water before extracting 250 mL samples under vacuum (10–15 mL/min). Elution is performed with methanol, and the eluate is dried under a 60–65 °C nitrogen stream. The final extract is reconstituted with internal standards in a 96/4 methanol/water mixture for LC-MS/MS analysis.

Použitá instrumentace

• Vacuum manifold and pump for SPE
• Bonded-phase SPE cartridges
• Nitrogen evaporator or heating block (60–65 °C)
• High-performance liquid chromatograph with binary pump
• Tandem mass spectrometer (LC-MS/MS) with ESI source and auto-tuning capability

Main Findings and Discussion

During IDC, calibration curves were established with at least five levels spanning a 20× range, forced through the origin, and evaluated using internal standard calibration. System blanks showed PFAS levels below one-third of the MRL. Seven replicates at MRL concentration met upper and lower prediction interval criteria (50–150 % recovery), while mid-range fortified samples demonstrated precision (RSD ≤ 20 %) and accuracy (±30 %). Peak asymmetry factors for the two earliest eluting analytes fell within 0.8–1.5, confirming adequate chromatographic performance. Routine batches maintain QC by interspersing continuing calibration checks (CCCs) every ten samples and verifying recoveries and relative percent differences (RPD ≤ 30 %).

Benefits and Practical Applications

• Regulatory compliance for drinking water quality monitoring
• High sensitivity and selectivity for trace PFAS detection
• Comprehensive QC framework ensures data integrity
• Adaptable extraction and calibration procedures for various laboratory settings

Future Trends and Possible Applications

Advancements may include automated SPE-LC-MS/MS platforms, miniaturized extraction formats to reduce solvent use, expanded target lists for emerging PFAS, and machine-learning tools for rapid data processing. Coupling to high-resolution mass spectrometry could further enhance identification of novel fluorinated contaminants.

Conclusion

EPA Method 537.1 provides a validated, reproducible protocol for quantifying selected PFAS in drinking water at sub-ng/L levels. Its rigorous QC measures and clear performance criteria make it a reliable choice for environmental laboratories and regulatory agencies.

References

• EPA Method 537.1: Determination of Selected Per- and Polyfluorinated Alkyl Substances in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry.
• Shimadzu Corporation. Handbook of Analysis Procedures for EPA Method 537.1, First Edition November 2022.