PTV On-Column Liner Gives You Two Inlets in One

Importance of the Topic

Programmable temperature vaporization (PTV) inlets offer a versatile platform for gas chromatography injections. By enabling cold on-column injections, the PTV On-Column liner protects thermally labile and low-volatility analytes, enhances sensitivity and reproducibility, and removes the need for a separate on-column inlet while reducing system costs.

Objectives and Study Overview

This application note evaluates a simple liner change that converts standard PTV hardware into a dual-mode inlet capable of true cold on-column injections. The study examines injector sealing, reproducibility using explosives as test compounds, and sensitivity improvements achieved at varying injection volumes.

Methodology and Instrumentation

• Inlet: Agilent PTV or Gerstel CIS4 equipped with PTV On-Column liner
• Columns: Rxi-5ms (6 m × 0.53 mm ID, 0.5 µm) or Rtx-TNT1 (6 m × 0.53 mm ID, 0.5 µm) with 5 m × 0.53 mm guard tubing
• Sample: EPA 8095 Explosives Calibration Mixes A and B diluted in acetonitrile
• Injection: splitless mode at 15 mL/min, 55 °C to 285 °C @10 °C/min (hold 10 min)
• Carrier gas: helium, constant flow (60 cm/s)
• Oven program: 50 °C to 280 °C @10 °C/min (hold 10 min)
• Detector: micro ECD at 300 °C with nitrogen make-up gas at 60 mL/min

Key Results and Discussion

• Seal integrity: The retention gap column pressed into the liner creates a leak-free interface.
• Reproducibility: RSD for nitroglycerin was 2.6 % absolute and 1.6 % relative; for TNT 1.5 % and 1.4 % respectively over five injections.
• Sensitivity across volumes: Linear response (r² = 0.9986 for TNB, r² = 0.9997 for TNT) achieved when injection volumes increased from 5 to 100 µL.
• Thermal protection: Cold on-column injection prevented flash vaporization, preserving labile compounds.

Benefits and Practical Applications

• Eliminates sample degradation and port activity issues.
• Supports larger injection volumes for improved limits of detection.
• Maintains high reproducibility and linear response.
• Reduces hardware costs by avoiding a second injection port.

Future Trends and Applications

As awareness of PTV expands in environmental, forensic, and industrial laboratories, potential developments include:

• Automation of cold on-column injection workflows.
• Custom liners for varying column dimensions and sample types.
• Integration with multi-detector platforms for comprehensive analysis.

Conclusion

A simple PTV On-Column liner conversion transforms a conventional PTV inlet into a dual-mode system, delivering cold on-column injection without additional hardware. This approach enhances sample integrity, reproducibility, and sensitivity while providing cost and workflow efficiencies.

References

• Explosives and Brominated Flame Retardant Analysis by Gas Chromatography with a New On-Column Injector Liner for a Programmable Temperature Vaporizing Injector
• Using Guard Columns and Retention Gaps in GC