Strategies for Ultimate Sensitivity of Per- and Polyfluoroalkyl Substances (PFAS) in Water

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are highly persistent environmental contaminants linked to adverse human and ecological health effects. Regulatory bodies have established extremely low advisory and enforceable limits for key PFAS in drinking water, underscoring the need for ultra-sensitive, reliable analytical methods.

Objectives and Study Overview

This study evaluates the performance gains of the 4th generation iFunnel on the Agilent 6495D triple quadrupole mass spectrometer compared with the previous 3rd generation model. Using US EPA Method 533, the work aims to demonstrate enhanced sensitivity, reduced background contamination, and robustness for routine PFAS monitoring at or below current advisory and proposed maximum contaminant levels.

Methodology and Instrumentation

Water matrices (bottled water, two tap sources, reagent blank) were spiked with native PFAS standards and isotopically labeled surrogates at low pg/mL concentrations. Samples underwent solid-phase extraction with the Agilent Bond Elut PFAS WAX cartridge. LC separations employed an Agilent Infinity II 1290 system with a Zorbax Eclipse Plus C18 column and PFC delay column. Mass spectrometric detection used electrospray ionization on Agilent 6495C (3rd gen) and 6495D (4th gen) instruments. A MassHunter Source Optimizer module refined source parameters, and narrow MS isolation widths were applied to eliminate specific interferences.

Main Results and Discussion

The 4th generation iFunnel achieved a 2.5–7× improvement in limits of quantitation (LOQ) across six PFAS compounds. Notably, PFOS LOQ decreased from 0.05 to 0.0075 ng/mL and PFOA from 0.005 to 0.0025 ng/mL. Chromatograms at LOQ levels exhibited clear, interference-free peaks with signal-to-noise ratios above 10 and relative standard deviations below 15% (n=8). Narrowing the MS resolution width effectively suppressed a low-level PFHxA interference without impacting analytical sensitivity. Environmental sample analysis showed no detectable PFAS in bottled water or blanks, while both tap water samples contained five of the six target compounds below proposed MCLs.

Benefits and Practical Applications

• Enables detection of PFAS at or below current EPA health advisory and proposed MCL thresholds.
• Supports routine implementation of EPA Method 533 without specialized large-volume injections or guard cartridges.
• Improves selectivity and reduces false positives by eliminating coeluting interferences.
• Offers a robust, high-throughput workflow for environmental monitoring, regulatory compliance, and water quality assurance laboratories.

Future Trends and Applications

Future developments may include expanded PFAS target lists covering next-generation and emerging analogues, integration of high-resolution mass spectrometry for non-target screening, further miniaturization of field-deployable platforms, and ongoing refinements in ion funnel and source technologies to push detection limits even lower.

Conclusion

The Agilent 6495D LC/TQ equipped with the 4th generation iFunnel significantly enhances sensitivity and selectivity for trace PFAS analysis in water. This advance facilitates compliance with stringent regulatory requirements and streamlines routine environmental monitoring workflows.

References

1. US EPA. Per- and Polyfluoroalkyl Substances (PFAS) in Drinking Water. https://www.epa.gov/pfas.
2. Agilent Technologies. Ultra-Trace Quantification of PFAS in Drinking Water. Application Note 5994-5797EN.
3. US EPA. Method 533: Determination of PFAS in Drinking Water by SPE and LC-MS/MS. Office of Water, 2019.