Expanding the Range of PFAS in a Single Injection to Include Ultra Short Chains Using the Atlantis™ BEH™ C18 AX Mixed Mode Column

Significance of the Topic

The expansion of analytical methods to include ultra-short chain PFAS (C2–C3) addresses critical gaps in environmental monitoring. Legacy long-chain PFAS regulations overlook these highly mobile, persistent compounds, leading to underestimation of total fluorinated contaminants.

Objectives and Study Overview

This study evaluated the mixed-mode Atlantis™ Premier BEH™ C18 AX column for one-shot LC-MS/MS analysis of PFAS ranging from C2 to C14 in diverse water matrices. Key aims were to assess retention of ultra-short PFAS, method performance against ASTM D8421 guidelines, and comparability to conventional C18 separations.

Methodology and Instrumentation

Samples, including landfill leachate, wastewater streams, and certified reference material (ERA 404), underwent direct dilution, methanol addition, filtration, and pH adjustment per ASTM D8421. Separation utilized an ACQUITY™ I-Class FTN system with Atlantis Premier BEH C18 AX column (2.1×100 mm, 1.7 µm) and Xevo™ TQ Absolute mass spectrometer in negative ESI mode. A dual-gradient of organic modifier and pH (ammonium hydroxide) optimized mixed-mode retention. Data processing followed ASTM quality control criteria in waters_connect™ software.

Main Results and Discussion

The mixed-mode column successfully retained ultra-short PFAS (TFA, PFPrA, PFPrS) that eluted near void volume on C18 alone. A pH-ramped gradient extended elution window from 3 min to 13 min, enhancing resolution of 46 PFAS. Following pH standardization of samples, retention times were stable within ±5%. Analysis of wastewater CRM showed agreement within certification limits and parity with reverse phase data, confirming accuracy and minimal matrix effects.

Benefits and Practical Applications

• Single-injection coverage of PFAS from C2 to C14 simplifies workflows and reduces instrument time.
• Improved chromatographic retention and peak shape of ultra-short PFAS lowers manual integration effort.
• Accurate quantitation in complex matrices supports regulatory compliance and environmental risk assessment.

Future Trends and Opportunities

Emerging needs include integration of high-throughput solid-phase extraction with mixed-mode separations, expansion to novel PFAS analogs, and coupling with total organic fluorine mass balance approaches. Advances in column chemistry may further improve selectivity and robustness for trace-level determinations.

Conclusion

The Atlantis Premier BEH C18 AX mixed-mode column enables comprehensive, reliable analysis of ultra-short to long-chain PFAS in a single LC-MS/MS run. Adoption of this method enhances environmental monitoring by capturing previously overlooked contaminants without compromising existing PFAS targets.

References

1. Ateia et al., Chemosphere, 2019;220:866–882.
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5. ASTM D8421-22, ASTM International, 2022.