FocusLiner™ Inlet Liners

Significance of the Topic

Effective gas chromatography (GC) injection relies on complete sample vaporization and consistent injection volume. Traditional inlet liners with wool plugs can suffer from displacement during repeated injections or sudden pressure changes, leading to poor reproducibility, solvent peak tailing, and mass discrimination. Innovations in inlet liner design are critical for achieving high precision and accurate quantitation in analytical laboratories.

Study Objectives and Overview

This study evaluates the performance of the FocusLiner™ inlet liner, which incorporates dual internal tapers to secure the wool plug, against conventional wool-plug liners and fixed sintered glass frit liners. The aim is to assess improvements in sample precision, accuracy, and solvent peak shape under repeated injections and pressure variations.

Methodology and Instrumentation

• FocusLiner design: dual tapered sections hold the wool plug in optimal position for needle penetration.
• Comparative testing: 4 mm I.D. traditional liners with displaced wool plugs, 4 mm I.D. FocusLiner liners, and 4 mm I.D. fixed frit liners.
• Evaluation metrics: percent relative standard deviation (%RSD) for probe compounds, solvent peak tailing, and peak area accuracy.
• Instrumentation used:
  
  • Agilent® 5890/6890/7890 GC systems
  • Shimadzu® GC-2010 and 14/15A/16 series
  • Thermo® ThermoQuest 8000/TRACE™ GC
  • Varian® 1075/1077 and CP-1177 Injectors
  • PerkinElmer® AutoSystem™ and Autosystem XL GC

Main Results and Discussion

• Wool plug stability: FocusLiner maintained correct plug position after repeated injections and pressure changes, preventing displacement observed in traditional liners.
• Reproducibility: FocusLiner achieved %RSD values around 0.2% for key probe compounds, compared to 8–10% with displaced plugs in standard liners—a 10- to 50-fold improvement.
• Solvent peak shape: Sharp, symmetrical solvent peaks were observed when the wool plug was correctly held, whereas displaced plugs caused significant tailing and potential interference with early-eluting analytes.
• Sample accuracy: Peak areas increased by approximately 25% with FocusLiner due to improved vaporization and consistent wiping of the needle tip.

Benefits and Practical Applications

• Enhanced sample vaporization and reduced mass discrimination in split and splitless injections.
• Consistent wiping action removes residual liquid from the needle tip, minimizing droplet formation and injection variability.
• High-temperature deactivation ensures chemical inertness and broad compound compatibility.
• Available in straight through, single taper, dual taper, and gooseneck formats, compatible with major GC platforms.
• Special FAST FocusLiner versions support fast GC columns (0.10–0.18 mm I.D.) for high-throughput applications.

Future Trends and Applications

Advancements in inlet liner design will focus on further minimizing dead volume, enhancing thermal transfer, and integrating microstructured surfaces to boost vaporization efficiency. Emerging applications include coupling with micro-GC and high-temperature sample introduction for complex matrices in environmental, petrochemical, and pharmaceutical analyses.

Conclusion

The FocusLiner inlet liner addresses the critical issue of wool plug displacement by securing the plug with dual tapers. This design delivers superior reproducibility, sharper solvent peaks, and enhanced sample accuracy without additional cost. Adopting optimized inlet liners is essential for reliable and high-sensitivity GC analysis.

References

• Sigma-Aldrich. FocusLiner™ Inlet Liners Product Information, 2008.