Agilent 6475 LC/TQ Performance Highlights with EPA Draft Method 1633 for Per and Polyfluoroalkyl Substances (PFAS) in Solid Samples

Importance of the Topic

The robust monitoring of per- and polyfluoroalkyl substances (PFAS) in soils and tissues is essential for understanding their environmental fate, human exposure pathways, and risk assessments. Draft EPA Method 1633 expands analytical requirements beyond aqueous matrices to solid samples, addressing growing regulatory and public health concerns over PFAS persistence and bioaccumulation.

Study Objectives and Overview

This application note evaluates the analytical performance of the Agilent 6475 triple quadrupole LC/MS paired with the 1290 Infinity II LC system for PFAS analysis in soil and fish matrices, following EPA Draft Method 1633. Key goals include:

• Assessing method transfer from Agilent 6470B to 6475 LC/TQ
• Validating calibration linearity, reproducibility, and sensitivity for 40 PFAS analytes
• Comparing soil quantification results across both instruments
• Demonstrating system robustness over >1,000 uninterrupted fish sample injections

Methodology and Instrumentation

Sample preparation combined isotopic dilution with a multi-step solid-phase extraction (SPE) cleanup using Bond Elut PFAS WAX cartridges. Soil extracts were fortified with internal standards, sequentially extracted with methanolic ammonium hydroxide, carbon sorbent treated, and filtered prior to analysis. Salmon tissue extracts were post-spiked and injected repeatedly to challenge system stability.

Instrumental Setup

The 1290 Infinity II LC employed a ZORBAX Eclipse Plus C18 analytical column and PFC delay guard, operating at 0.4 mL/min with a 5-minute gradient. The 6475 LC/TQ used Agilent Jet Stream electrospray in negative mode. Automated AI-driven source optimization and method development features reduced manual tuning time. Key parameters such as gas temperature (230 °C), gas flows, and MRM transitions were imported directly from the Agilent PFAS database.

Main Results and Discussion

Calibration across 0.1–1,000 ng/mL exhibited R² values >0.995 and replicate RSDs <14%. Method transfer between 6470B and 6475 showed nearly identical linearity and sensitivity. Soil spike recoveries ranged 70–130% with RSDs <20% on both systems, averaging 97–103% recovery. Over 1,300 salmon matrix injections, calibration verification standards remained within ±20% of nominal abundance for most analytes; 86% of compounds maintained <10% RSD, while thermally sensitive FTS and FOSAA classes showed slightly higher variability (16–22%).

Benefits and Practical Applications

• Seamless method transfer ensures laboratories can upgrade instruments without revalidation burdens.
• AI-based optimization streamlines tuning, improving throughput and consistency for large-scale monitoring.
• Proven robustness supports high-volume routine analysis in environmental and food safety laboratories.

Future Trends and Potential Applications

Advancements in AI-guided method development are expected to extend to additional contaminant classes and complex matrices. Integration of high-resolution mass spectrometry, automated sample handling, and expanded PFAS databases will further enhance sensitivity and reduce analyst workload. Routine EPA 1633 compliance may drive standardized multi-laboratory data comparability and emerging regulatory guidelines for non-aqueous samples.

Conclusion

The Agilent 6475 LC/TQ coupled with the 1290 Infinity II LC delivers reliable, high-throughput PFAS analysis in solid and tissue samples per EPA Draft Method 1633. Its seamless method transfer, precise quantitation, and sustained robustness position it as a valuable tool for environmental, food safety, and regulatory laboratories.

References

• U.S. EPA. Draft Method 1633: Analysis of Per- and Polyfluoroalkyl Substances in Solid and Tissue Samples by LC-MS/MS. EPA 821-D-21-001, August 2021.
• U.S. EPA. Our Current Understanding of the Human Health and Environmental Risks of PFAS. March 2023.
• Hunt, K. et al. Analysis of PFAS in Aqueous Samples per EPA Draft Method 1633. Agilent Application Note 5994-4926EN, 2022.
• Giardina, M. Analysis of PFAS in Soil Extracts. Agilent Application Note 5994-2999EN, 2021.
• Yang, X. A Fast Sample Preparation Workflow for Veterinary Drugs Analysis in Salmon. Agilent Application Note 5994-1124EN, 2019.