The Determination of 40 Per- and Polyfluoroalkyl Substances in Biosolids

Importance of the topic

The presence of per- and polyfluoroalkyl substances in biosolids presents a significant analytical challenge due to their complex organic and inorganic composition. Accurate PFAS quantitation is critical for environmental monitoring, regulatory compliance, and safe land application of treated sewage sludge.

Objectives and study overview

This study adapts EPA Method 1633 sample preparation for biosolids by introducing a dual‐phase SPE cartridge with blended WAX/Carbon S sorbents and implementing a post‐extraction EMR PFAS Food II cleanup. NIST SRM 2781 domestic sludge served as the matrix analogue to assess method performance.

Methodology and instrumentation

• Dual-phase SPE: Agilent Bond Elut PFAS WAX/Carbon S (200 mg WAX/50 mg Carbon S) cartridges optimized for permeability and reduced clogging.
• Matrix reduction: Agilent Captiva EMR PFAS Food II cartridges replaced syringe filtration to remove coextractives.
• LC/MS/MS: Agilent 1290 Infinity II LC system with PFAS analysis conversion kit coupled to 6475A triple quadrupole MS with Jet Stream ESI. Optimized MRM transitions applied via the extended PFAS database.
• Quantitation: Stable‐isotope dilution using EIS and NIS, 1/x weighted regression (linear or quadratic), LOQ defined by lowest calibrator.

Key results and discussion

• Permeability: Blended WAX/Carbon S cartridges exhibited higher flow rates and withstood 50 mL loadings without clogging, outperforming layered formats.
• Matrix effects: EMR cleanup effectively removed interferences (e.g., PFHxS, PFOS), restored accurate EIS signals, and eliminated signal suppression.
• Accuracy and precision: Measurements of certified PFAS in SRM 2781 were within ±10% of reference values after EMR cleanup, compared to significant biases without cleanup.
• Matrix spikes: Over 35 PFAS targets met EPA acceptance criteria (<30% RSD) when processed with EMR, demonstrating consistent recoveries across diverse analytes.

Benefits and practical applications

• A streamlined workflow combining blended SPE and EMR cleanup reduces filtration steps and manual handling.
• Enhanced throughput and reproducibility support routine PFAS monitoring in biosolids, soils, and other solid matrices.
• Method alignment with EPA Method 1633 facilitates regulatory acceptance and interlaboratory comparability.

Future trends and opportunities

• Automation of SPE and EMR steps to further increase sample throughput and reduce analyst variability.
• Development of novel sorbents and hybrid cleanup cartridges for expanded PFAS coverage and selectivity.
• Integration with high-resolution mass spectrometry for non‐target screening of emerging fluorochemicals.
• Standardization of protocols and participation in proficiency testing to ensure global method harmonization.

Conclusion

The integration of Agilent Bond Elut blended PFAS WAX/Carbon S cartridges with Captiva EMR PFAS Food II cleanup enhances PFAS recovery accuracy, precision, and robustness in biosolids. This modified EPA 1633 workflow provides a reliable, high-throughput solution for complex solid matrices and supports expanded environmental monitoring efforts.

References

• U.S. EPA Method 1633A: Analysis of PFAS in Environmental Samples, December 2024.
• 40 CFR Part 503: Sewage Sludge Use or Disposal Standards, EPA, 2023.
• U.S. EPA, Basic Information about Biosolids, 2025.
• Patel S. et al., Rev. Environ. Sci. Biotechnol. 2020, 19, 807–841.
• NIST SRM 2781 Certificate of Analysis, 2020.
• Saliu T.D. et al., J. Hazard. Mater. 2024, 480, 136170.
• Zhao L., Agilent Application Note 5994-8777EN, 2025.
• DoD Data Validation Guidelines Module 6 for PFAS Analysis, 2022.