Enhanced screening of PFAS compounds in wastewater: Implementing U.S. EPA Method 1621 with improved combustion-ion chromatography

Importance of the topic

Per- and polyfluoroalkyl substances (PFAS) represent a widespread group of persistent fluorinated chemicals that bioaccumulate and pose environmental and health risks. Screening wastewater for total adsorbable organic fluorine (AOF) offers a rapid non-targeted approach to estimate overall PFAS burden. Implementing U.S. EPA Method 1621 with improved combustion-ion chromatography (C-IC) enhances sensitivity, reduces contamination, and streamlines analysis for routine monitoring.

Study objectives and overview

This work demonstrates the application of EPA Method 1621 using a complete C-IC workflow. Key goals include:

• Minimizing baseline fluorine contamination through optimized adsorption and combustion design.
• Improving sensitivity and reproducibility compared with previous implementations.
• Validating method performance (retention, calibration, precision, accuracy, detection limits) for wastewater screening.

Methodology and instrumentation used

Samples (municipal water, blended wastewater, pond water) and blanks are spiked or left unmodified, adjusted with sodium nitrate, and loaded (100 mL) onto granular activated carbon (GAC) via the Thermo Scientific Cindion C-IC adsorption module (six-position semi-automated). Adsorbed organofluorine is combusted in a Cindion C-IC combustion/absorption system with a Z-fold tube design for efficient HF generation. Resulting fluoride is quantified by Dionex Inuvion RFIC with suppressed conductivity detection. Key components include:

• Cindion Combustion/Absorption Module and GAC columns
• Dionex Inuvion RFIC system with IonPac AG24/AS24 columns, EGC 500 KOH eluent generator, CR-ATC 600 trap, and ADRS 600 suppressor
• Chromeleon CDS software for unified control and data processing

Main results and discussion

Retention time windows for fluoride (3.35–3.75 min) and chloride met EPA criteria. Calibration used a quadratic fit with area weighting (1/A^2), yielding a relative standard error (RSE) of 5.75% (<20% limit). Initial demonstration of accuracy and precision showed 103% recovery and 4.5% RSD. Method blanks averaged ~2.17 µg/L fluoride; the method detection limit (MDL) was 1.7 µg/L. Real samples contained total AOF of 0.29–4.86 µg/L. Spike recoveries of PFHxS equivalent fluorine ranged from 82% to 101%, confirming method accuracy. Compared with previous work, the optimized C-IC workflow reduced contamination, improved MDLs, and maintained reproducibility.

Practical benefits and applications

The integrated C-IC solution offers:

• Enhanced throughput: semi-automated adsorption of six samples per cycle.
• Reduced footprint and contamination sources via compact Z-fold combustion and streamlined flow path.
• Unified software control for simplified operation and data management.
• Robust screening of PFAS in diverse aqueous matrices to support environmental monitoring, industrial compliance, and research.

Future trends and applications

Ongoing development may include:

• Extension to solid, biosolid, and tissue matrices under EPA Method 1633.
• Coupling with high-resolution mass spectrometry for targeted/non-targeted PFAS speciation.
• Further miniaturization and automation for field-deployable screening.
• Integration into large-scale monitoring networks and regulatory frameworks.

Conclusion

The optimized C-IC workflow implementing EPA Method 1621 effectively screens PFAS as AOF in wastewater. It achieves low detection limits (1.7 µg/L), high accuracy (82–101% recovery), and precision (RSD <5%), while reducing contamination and instrument footprint. This approach supports rapid environmental assessment and regulatory compliance.

References

• U.S. EPA. Method 1621: Determination of Adsorbable Organic Fluorine (AOF) in Aqueous Matrices by Combustion-Ion Chromatography. EPA 821-R-24-002. Washington, DC, January 2024.
• Christison T., Rumachik N. Thermo Fisher Scientific Application Note AN002748: Results from EPA Method 1621 Collaboration Study. 2024.
• Christison T., Rumachik N. Thermo Fisher Scientific Technical Note TN003056: Implementation Tips for EPA Method 1621. 2024.
• Lord H. et al. Total Organofluorine (TOF) Analysis by Combustion-Ion Chromatography. NEMC 2022 Poster.
• Jones J.L., Burket S.R., Hanley A., Shoemaker J.A. Standardized AOF Screening Method for Wastewaters. Analytical Methods, 2022.
• Han Y., Pulikkal V.F., Sun M. Validation of AOF Analysis and Comparison of PFAS Methods in Water. ACS EST Water, 2021, 1, 1474–1482.