Importance of Liner Selection in Aqueous Solution Analysis

Significance of the Topic

Gas chromatography is widely used for low-level compound analysis. When water-rich samples are injected, solvent effects often distort peak shapes and reduce repeatability. Optimizing inlet liner design is essential to ensure consistent vaporization and reliable results in aqueous solution analysis.

Objectives and Study Overview

The study aimed to develop a novel GC inlet liner tailored for aqueous sample injection and to evaluate its performance against a conventional liner. Two test cases were selected: ethanol determination in sanitizer gel via TCD detection and ethanol analysis in liquor samples via FID. Comparative assessments focused on peak shape, separation from water, system suitability, and repeatability.

Instrumentation

• Shimadzu Nexis GC-2030 gas chromatograph with AOC-30i autosampler
• Special aqueous solution liner (P/N: 227-35015-01) containing 20 mg deactivated glass wool positioned 20 mm from the top
• Standard GC sample liner (P/N: 227-35007-01) for baseline comparison
• Thermal Conductivity Detector (TCD) for Evaluation A and Flame Ionization Detector (FID) for Evaluation B
• Capillary columns: SH-624 (0.53 mm I.D. × 30 m, 3 µm) and SH-1 (0.53 mm I.D. × 30 m, 3 µm)
• Shimadzu Xtra Life Microsyringe 10 µL
• Carrier gases: Helium for make-up and column flow; Hydrogen and Air for FID

Main Results and Discussion

• The special liner significantly reduced peak tailing of ethanol and water peaks compared to the standard liner, yielding sharper, more symmetrical peaks.
• In the sanitizer gel assay, the special liner achieved an ethanol area %RSD of 1.44% (n=10) versus 16.34% with the standard liner, while meeting system suitability criteria (resolution, tailing factor).
• For liquor matrices, calibration curves with the special liner showed linearity (R2 > 0.9999) and area %RSD values below 1.6% across 5–20% ethanol concentrations, outperforming the standard liner which exhibited up to 9.36% RSD.
• The optimized liner design stabilized sample vaporization, improving reproducibility and analytical robustness in water-based samples.

Benefits and Practical Applications

• Improved quantitative reliability for ethanol and other volatiles in high-water content samples.
• Simplified integration into existing GC workflows through direct liner replacement.
• Applicable to quality control in pharmaceutical, food and beverage, and environmental laboratories.

Future Trends and Potential Applications

Increasing focus on tailored inlet liners may extend to other challenging matrices such as high-boiling solvents or viscous media. Integration with mass spectrometry detection and high-throughput autosamplers could further enhance analytical efficiency. Additionally, development of eco-friendly liner materials and coatings may align with green chemistry initiatives.

Conclusion

The special liner for aqueous solutions demonstrated superior peak shapes, repeatability, and system suitability compared to a standard GC liner under both TCD and FID detection modes. Routine use in water-rich sample analysis can improve data quality, with recommended liner replacement after 50–100 injections to maintain performance.