Evaluation of the Ultra Inert Liner Deactivation for Active Compounds Analysis by GC

Significance of the topic

Gas chromatography of reactive or labile compounds, such as pesticides and semivolatiles, requires a completely inert flow path to prevent adsorption, degradation and poor quantitative performance. The inlet liner is a critical point of contact where active sites can cause analyte loss or breakdown. Evaluating and improving liner deactivation chemistry directly enhances sensitivity, linearity and robustness in environmental, food, pharmaceutical and industrial analyses.

Study objectives and overview

This study compares the performance of the newly developed Agilent Ultra Inert deactivated inlet liner with existing commercial liner chemistries. Two probe tests were used: endrin and DDT breakdown over 100 splitless injections, and semivolatile active compound analysis via USEPA Method 8270 over a 2–80 ng on-column calibration range. Stability of deactivation and analytical reproducibility were key evaluation criteria.

Materials and methods

• Chemicals: Endrin and DDT standards in isooctane; 8270 semivolatile multi-component standard in methylene chloride with internal standards.
• Breakdown test: 50/100 ppb Endrin/DDT solution injected in splitless mode. One standard followed by nine solvent blanks, repeated for 100 cycles, with breakdown calculated as percent of degradation products (EA+EK or DDE+DDD) over total peak area.
• Semivolatile test: USEPA 8270 short test mix containing nitrophenols, amines, phenolics and polyaromatics. Calibration standards at 2, 5, 20, 40, 80 µg/mL prepared; 1 µL injections on FID. Response factors and RSDs calculated across calibration range.
• Comparison: Ultra Inert liners (n=16) vs Agilent proprietary (n=8), Restek Siltek (n=8), Restek Sky (n=4) and SGE (n=4) under identical splitless conditions.

Used instrumentation

• GC systems: Agilent 7890 GC with 7683B autosampler; µECD for breakdown test; FID for semivolatile test.
• Columns: HP-5MS UI (15 m × 0.25 mm, 0.25 µm) for µECD; Ultra 2 (25 m × 0.32 mm, 0.52 µm) for FID.
• Consumables: Single-taper splitless liners, septa, Vespel/graphite ferrules, amber vials and polymer feet inserts.

Main results and discussion

• Endrin/DDT breakdown: Ultra Inert liners exhibited 1.2% Endrin and 2.5% DDT breakdown on injection 1, rising to 12.2% and 3.0% on injection 101. All values remained below the 20% threshold, outperforming SGE and matching or surpassing other deactivations in stability.
• Semivolatile active compounds: Across 2–80 ng on-column, all target analytes showed RSD <20% for response factors. The most challenging analyte, 2,4-dinitrophenol, delivered a mean RF of 0.288 with 15.6% RSD, higher and more consistent than competing liners.
• Liner comparison: Ultra Inert deactivation provided the highest response factors for key active compounds, particularly 2,4-DNP at low concentrations (e.g. 0.5 ppm SIM mode), while Restek Sky liners showed lower responses and higher variability for basic analytes such as benzidine.

Benefits and practical applications

• Enhanced inertness reduces analyte degradation and adsorption, improving sensitivity and calibration linearity in trace pesticide and semivolatile analysis.
• Robust performance over many injections lowers maintenance frequency and extends liner lifetime.
• Compatible with universally used splitless injection and readily integrates into existing GC workflows for environmental, food safety, pharmaceutical and industrial quality control.

Future trends and opportunities

• Development of next-generation deactivation chemistries to extend inertness to emerging compound classes (e.g. polar, highly active pharmaceuticals).
• Integration of on-column injection and advanced column coatings to further mitigate inlet contributions.
• Adoption of digital monitoring of liner performance and predictive maintenance in automated laboratory environments.
• Expansion to GC-MS/MS and high-resolution mass spectrometry platforms for ultra-trace analysis.

Conclusion

Agilent Ultra Inert deactivated inlet liners demonstrate superior inertness and stability for active compound analysis by GC. In probing tests with endrin/DDT breakdown and USEPA 8270 semivolatile analytes, Ultra Inert liners maintained breakdown and response factor variability well below 20% over extended use. Their high sensitivity and reproducibility make them well suited for demanding analytical applications.

References

• USEPA. Method 8270D: Semivolatile Organic Compounds by GC/MS; EPA SW-846.
• Zhao L., Broske A.D., Mao D., Vickers A. Improvements in Agilent 6890/5973 GC/MSD for USEPA Method 8270. Agilent Technol. Publ. 5988-3072EN, 2011.