Detection of Impurities in Breathing Oxygen by Pulsed Discharge Detector (PDD)

Importance of the Topic

Breathing oxygen of the Avio grade must have extremely low levels of impurities to ensure safety and performance in medical, military aviation and critical industrial applications.

Objectives and Study Overview

This application note describes a method using the Thermo Scientific TRACE 1310 Series GC with an Instant Connect Pulsed Discharge Detector (PDD) and auxiliary oven to identify and quantify trace contaminants in avio oxygen.

Methodology and Instrumentation

The system comprises:

• Thermo Scientific TRACE 1310 GC
• Pulsed Discharge Detector (PDD) Module with helium discharge (30 mL/min) and Hopfield emission ionization (13.5–17.7 eV)
• Six-port sampling valve (250 µL loop) and ten-port column-switching valve, both helium-purged
• Columns: 30 m × 0.53 mm TG Bond MSieve for O₂, N₂, CH₄, CO; 30 m × 0.53 mm TG Bond Q for CO₂, N₂O, C₂ hydrocarbons
• Isothermal operation at 30 °C, carrier pressure 150 kPa, auxiliary gas pressure 50 kPa, split ratio 1/10

Results and Discussion

• Four-point calibration for CO₂, N₂O, C₂H₂, C₂H₄, C₂H₆, CH₄ and CO showed excellent linearity (R² > 0.997).
• Method detection limits ranged from 0.6 pg (C₂H₄) to 4.0 pg (N₂O) at low ppm levels.
• Peak area repeatability RSDs were below 1.2% and retention time RSDs below 0.1%, demonstrating high precision.

Practical Benefits and Applications

The modular PDD design allows rapid installation, minimal maintenance and continuous operation, fully meeting pharmacopoeia requirements for oxygen certification and ensuring reliable trace impurity monitoring.

Future Trends and Perspectives

Potential developments include real-time, point-of-use gas purity monitoring, integration with automated QA/QC workflows, extension of the method to other high-purity gases and coupling with mass spectrometry for enhanced molecular identification.

Conclusion

The TRACE 1310 GC equipped with a PDD and auxiliary oven provides a robust, ultra-sensitive, and user-friendly solution for detecting and quantifying impurities in breathing oxygen, supporting critical applications that demand the highest gas purity.