Evaluation of Fused Silica Tubing for Active Compound Analysis in an Inert Flow Path

Significance of the topic

Precise analysis of active compounds by gas chromatography relies on an inert flow path that minimizes analyte degradation, peak tailing, and breakdown. Deactivated fused silica tubing used as guard columns protects the analytical column, extends its lifetime, and enhances chromatographic performance. This study evaluates Agilent Ultimate Plus deactivated fused silica tubing against competitive products under identical conditions to demonstrate its inertness advantages.

Objectives and study overview

The main goals of this investigation were to:

• Compare the inertness of Agilent Ultimate Plus tubing with deactivated tubing from two other suppliers.
• Use qualitative (peak shape) and quantitative (tailing factor, breakdown) probes to assess performance.
• Assess long-term stability over multiple injections.

Methodology and instrumentation

Chromatographic analyses were conducted on an Agilent 7890B GC equipped with microcell ECD and FID detectors. A 7683B autosampler and split/splitless inlet delivered samples. Guard columns tested included 5 m Agilent Ultimate Plus tubing (0.25 mm and 0.32 mm i.d.) and equivalent lengths from suppliers P and R. The analytical column was Agilent J&W HP-5ms Ultra Inert. Inertness was probed using:

1. An inert test mixture of basic, polar, and phosphorylated compounds to evaluate tailing factors.
2. Phenols EPA Method 604 acidity standard to assess peak symmetry and repeatability.
3. Endrin/DDT breakdown following EPA Method 8081B to monitor degradation over 70 injections.

Main results and discussion

Agilent Ultimate Plus tubing delivered the most symmetrical peaks, with tailing factors (Tf) close to unity (1.05–1.50), whereas competitors exhibited significant tailing (Tf up to 5.4) for trimethyl phosphate. In acidity tests, the Agilent tubing maintained low RSD (< 7%) for the most active phenols and superior signal intensity. During endrin/DDT breakdown, Ultimate Plus tubing kept endrin degradation below 7.5% and DDT below 3% after 71 injections, remaining well within regulatory limits, while other tubing exceeded 15% endrin breakdown after 50 runs.

Benefits and practical applications

• Enhanced peak symmetry and sensitivity for challenging active analytes.
• Extended analytical column life by isolating contamination in the guard segment.
• Reliable quantitative performance and trace-level detection in environmental, food, and pharmaceutical analyses.

Future trends and potential applications

Advances in surface deactivation chemistries are expected to further improve inertness, enabling more robust analysis of highly active polar compounds and environmental contaminants. Integration with GC/MS workflows and high-throughput screening platforms will broaden applications in regulatory, pharmaceutical, and agrochemical laboratories.

Conclusion

Agilent Ultimate Plus deactivated fused silica tubing outperformed competing guard column options in inertness, peak shape, and long-term stability, making it an excellent choice for high-sensitivity GC and GC/MS analyses of active compounds.

References

1. Agilent Technologies. Agilent J&W GC Column Selection Guide, Publication 5990-9867EN, 2012.
2. Agilent Technologies. Deactivated Ultimate Plus Fused Silica Tubing Technical Overview, Publication 5991-5142EN, 2014.
3. Dang NA. Better Pesticide Analysis with Agilent J&W Ultimate Plus Tubing, Application Note 5991-5404EN, 2014.
4. Dang NA. Analyze Semivolatiles with Agilent J&W Ultimate Plus Tubing, Application Note 5991-5441EN, 2014.
5. Dang NA. Analyze Drugs of Abuse with Agilent Ultimate Plus Tubing, Application Note 5991-5303EN, 2014.