Using the Combined Peak Capacity of Liquid Chromatography and Cyclic Ion Mobility Mass Spectrometry to Enhance PFAS Analysis Efficiency and Specificity

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants linked to adverse health effects such as cancer and immune disorders. Regulatory bodies worldwide are tightening limits on PFAS in water, food and biological matrices, driving the need for analytical methods that combine high throughput with superior specificity. Liquid chromatography–ion mobility–mass spectrometry (LC-IM-MS) with cyclic ion mobility offers enhanced peak capacity to resolve isomeric and isobaric PFAS species, improving both screening and quantitation in complex samples.

Objectives and Study Overview

This study demonstrates how a combined approach using ultra-high-performance liquid chromatography (UHPLC) and cyclic ion mobility (SELECT SERIES™ Cyclic™ IMS) can:

• Reduce PFAS analysis time by 75%
• Resolve coeluting linear and branched perfluorooctanesulfonic acid (PFOS) isomers in human serum
• Differentiated isobaric cholic acid biomarkers
• Enable quantitation of individual PFOS isomers via non-targeted screening workflows

Methodology and Applied Instrumentation

Human serum samples were extracted using a mixed-mode SPE 96-well µElution plate. Reversed-phase UHPLC separations employed an ACQUITY Premier system with Atlantis™ Premier BEH™ C18 AX isolator column (2.1×50 mm, 5 µm) and a shortened gradient at 0.6 mL/min. Ionization was by negative-mode electrospray. Separations were performed on a Waters ACQUITY UPLC Premier HSS T3 column coupled to a SELECT SERIES Cyclic IMS. MassLynx™ 4.2 controlled data acquisition and waters_connect™ 3.1 managed ion mobility processing. A PFAS collision cross section (CCS) library (130 entries) supported compound identification.

Main Results and Discussion

By combining chromatographic retention, m/z and ion mobility separation (R~145–250), the workflow achieved:

• 75% reduction in run time (from 22 min to 5.5 min) without loss of isomer resolution
• Baseline separation of coeluting PFOS linear and branched isomers via their distinct arrival time distributions (ATDs)
• Resolution of isobaric cholic acid biomarkers at R~250 in a UHPLC timeframe (3 s peak width)
• Quantitation of three PFOS isomers in anonymized human serum by constructing calibration curves from a linear PFOS standard containing known branched isomer ratios

The cyclic IMS system’s ability to dial up resolution allowed single-component fragmentation spectra for each isomer and reliable CCS measurements to confirm identity at low abundance.

Benefits and Practical Applications

The integrated LC-IM-MS approach provides:

• High peak capacity to distinguish isobaric and isomeric PFAS without extended chromatographic gradients
• Rapid non-targeted screening to detect known, emerging and unknown PFAS in environmental and biological samples
• Quantitative capability for individual isomers, enabling correlation of isomer profiles with biological effects
• Reduced false positives through orthogonal separation dimensions

Future Trends and Applications

As PFAS regulations evolve and the number of target compounds expands, non-targeted high-capacity methods will become indispensable. Future developments may include:

• Expanded CCS libraries for emerging PFAS and transformation products
• Automation of data processing and chemometric tools for rapid screening
• Integration with high-resolution tandem MS for structural elucidation
• Portable or miniaturized IM-MS platforms for field monitoring

Conclusion

The combined UHPLC and cyclic IM-MS workflow delivers significant gains in throughput and specificity for PFAS analysis. With 75% shorter runtimes and full resolution of isomeric PFOS and isobaric biomarkers, this approach complements existing regulatory methods and enables deeper insight into PFAS exposure and toxicity.

Reference

1. McCullagh M. et al. Enhanced Specificity for PFAS Analysis Using Cyclic IMS CCS. Waters Application Note, 2024.
2. U.S. EPA Method 1633: Non-Targeted Analysis of PFAS in Environmental Media, 2024.
3. Directive (EU) 2020/2184 on Drinking Water Quality, 2020.
4. Kirkwood-Donelson KI et al. Nontargeted IM-MS Analyses of PFAS. Sci. Adv. 9(43):eadj7048, 2023.
5. Zhang X. et al. PFAS Exposure and Fatty Liver Disease Risk. JHEP Reports 5(5):100694, 2023.