Manual Extraction of PFAS in Drinking Water in Compliance with ISO 21675

Significance of the Topic

Per- and polyfluorinated alkyl substances (PFAS) are persistent environmental contaminants with documented health risks. Their chemical stability and widespread use in industrial and consumer products have led to accumulation in water supplies, creating a demand for reliable monitoring methods. ISO 21675 provides a standardized protocol for quantifying PFAS in drinking water, ensuring data comparability and regulatory compliance.

Objectives and Study Overview

This application note describes the development and validation of a manual solid‐phase extraction (SPE) procedure for PFAS in drinking water according to ISO 21675. Key goals include:

• Implementing a vacuum‐driven SPE workflow using PFAS‐free components
• Optimizing extraction conditions to achieve low method detection and reporting limits
• Demonstrating accuracy, precision, and minimal background contamination

The study employs Biotage VacMaster vacuum manifold and PFAS‐specific SPE columns, followed by concentration with the TurboVap LV and analysis by LC‐MS/MS.

Methodology and Instrumentation

The extraction sequence involves sample acidification, SPE conditioning, loading, washing, drying, and elution:

• Reagents:
   • Ammonium hydroxide in methanol (0.1 %) for column conditioning and elution
   • Acetate buffer (20 mM ammonium acetate, pH ~4) for sample wash steps
   • Glacial acetic acid for pH adjustment to 3
• SPE Components:
   • Biotage VacMaster 20 Sample Processing Station with PFAS‐free stopcocks and VacMaster LVE Kit accessories
   • EVOLUTE PFAS SPE cartridges (500 mg/6 mL and 150 mg/6 mL formats)
• Evaporation:
   • TurboVap LV Automated Solvent Evaporation System with 48‐position rack
   • Concentration to ~1 mL under nitrogen at 60 °C
• LC-MS/MS Analysis:
   • Agilent 1290 Infinity II UHPLC with InfinityLab PFC Delay Column and ZORBAX RRHD Eclipse Plus C18 (2.1×50 mm, 1.8 µm)
   • Agilent 6470 Triple Quadrupole MS in negative electrospray mode
   • Mobile phases: 20 mM ammonium acetate (A) and methanol (B) at 0.2 mL/min, with gradient from 95 % A to 100 % B

Main Results and Discussion

System performance and method validation demonstrated:

• Calibration linearity over 0.2–20 ppt for 30 PFAS analytes, with R² > 0.99 when forced through zero.
• Minimum Reporting Level (MRL) of 2 ng/L achieved for all targets; recoveries within ±15 % and CVs below 10 % using both 150 mg and 500 mg cartridges.
• Low process background verified by system blanks, evaporation blanks, and full laboratory reagent blanks; all PFAS signals < 1/3 MRL.
• Carryover assessment after four 50 ng/L fortified samples showed negligible analyte carryover, typically < 0.3 ng/L.
• Initial Demonstration of Precision and Accuracy (IDP/IDA) at 15 ng/L confirmed mean recoveries of 90–110 % and CV < 10 % for all analytes.

Benefits and Practical Applications

This SPE‐based workflow offers:

• High sensitivity and reproducibility suitable for routine water monitoring laboratories.
• PFAS‐free hardware and consumables to minimize background contamination.
• Flexibility in cartridge format for variable sample volumes and analyte load.
• Compatibility with standard LC-MS/MS platforms, facilitating adoption without major instrumentation changes.

Future Trends and Opportunities

Emerging directions in PFAS analysis include:

• Automated SPE and on‐line cleanup systems to increase throughput and reduce manual steps.
• High‐resolution mass spectrometry for non‐target screening of novel PFAS homologues.
• Advanced sorbent materials and mixed‐mode cartridges to extend analyte scope.
• Integration of data analytics and AI‐driven quality control for real‐time result assessment.

Conclusion

The manual extraction protocol described here, adhering to ISO 21675, reliably quantifies a broad spectrum of PFAS at sub‐ppt to low‐ppt levels in drinking water. The combination of PFAS‐free SPE cartridges, robust vacuum manifold workflows, and sensitive LC-MS/MS detection meets stringent regulatory requirements and supports environmental monitoring needs.

References

• ISO 21675:2019, Water Quality – Determination of Per‐ and Polyfluoroalkyl Substances (PFAS) in Drinking Water by Solid Phase Extraction and LC-MS/MS.
• Biotage Application Note AN967, Manual Extraction of PFAS in Drinking Water in Compliance with ISO 21675, 2022.