Recommended Plumbing Configurations for Reduction in Per/Polyfluoroalkyl Substance Background with Agilent 1260/1290 Infinity (II) LC Systems

Significance of the topic

Per- and polyfluoroalkyl substances (PFAS) are persistent, bioaccumulative environmental contaminants of growing concern. Their strong C–F bonds confer stability but also complicate ultra-trace analysis. Minimizing background PFAS from chromatographic systems is critical for sensitive detection at ng/L levels.

Objectives and overview of the study

This application note outlines the sources of PFAS contamination in Agilent 1260 and 1290 Infinity II liquid chromatography systems and presents a set of modifications to achieve a fluoropolymer-free flow path. The goal is to reduce background signals and enable reliable quantification of PFAS following EPA Method 537 guidelines.

Methodology

Key system modifications:

• Replace solvent bottle caps and inlet lines: switch from PTFE to PEEK tubing and polypropylene caps.
• Remove PTFE filter frits in pump heads and purge valves; bypass degasser to direct PEEK lines to the pump.
• Install a delay column (ZORBAX Eclipse Plus C18, 4.6×50 mm, 3.5 µm) between pump and injector for background separation.
• Modify autosampler components: use PEEK rotor seals, replace PTFE vent lines, and select PTFE-free vials, caps, and septa.
• Implement extended multiwash cycles (15–20 s) to mitigate PFAS carryover on the needle and seat.

Instrumentation used

• Agilent 1260 Infinity II or 1290 Infinity II LC system with high-speed pump and multisampler/autosampler.
• PEEK tubing (1/8”×0.062” id), polypropylene GL45 bottle caps, stainless steel inlet filters.
• Agilent ZORBAX Eclipse Plus C18 delay column (p/n 959943-902).
• Stainless steel filter sinkers, PEEK threaded fittings, ferrules, and lock rings.
• PTFE-free autosampler vials (1 mL) with polypropylene septa.

Main results and discussion

System baseline analysis showed a marked reduction in PFAS background after fluoropolymer removal. Coupling the modified LC to a Q-TOF MS eliminated contaminant peaks observed in the unmodified system. The delay column effectively separated residual PFAS background from analyte peaks, as demonstrated with PFOS. These modifications enabled trace-level quantitation down to EPA advisory limits (20–400 ng/L) without interfering signals.

Benefits and practical applications

• Enhanced sensitivity and lower detection limits for PFAS in water, soil, sludge, and biota.
• Robust workflow for dedicated trace analysis laboratories and QA/QC environments.
• Compatibility with multi-method LC systems via optional delay column installation.

Future trends and potential applications

Ongoing developments may focus on fully fluoropolymer-free chromatography systems, automated tubing and component changeovers, and integration with high-resolution mass spectrometry workflows. Emerging PFAS analogs will require adaptive background removal strategies and dedicated analytical protocols.

Conclusion

Implementing PEEK and polypropylene replacements, removing PTFE frits, and employing a delay column significantly reduces PFAS background in Agilent Infinity II LC systems. These modifications support ultra-trace PFAS analysis in compliance with regulatory advisories and enhance analytical confidence.