Ammonia Analysis Using the Agilent 990 Micro GC

Significance of the topic

Ammonia is a key compound in agriculture, refrigeration, detergents and chemical manufacturing. Accurate and stable measurement of ammonia levels is essential for process control, safety, and environmental monitoring. Traditional micro-GC columns often suffer from peak tailing and retention time shifts, especially at low concentrations, compromising quantitative reliability.

Objectives and Study Overview

This application note evaluates the performance of the Agilent 990 Micro GC equipped with a J&W CP-Volamine column for ammonia analysis. The goals are to demonstrate:

• Reliable quantification of low (100 ppm) and high (20%) ammonia standards
• Stable analysis of real sample vapors containing saturated water and ~10% ammonia
• Long-term inertness and repeatability over six months of consecutive injections

Methodology and Instrumentation

The micro-GC system and analytical conditions:

• Instrument: Agilent 990 Micro GC
• Column: 15 m J&W CP-Volamine straight channel (nonpolar MPD-deactivated stationary phase)
• Carrier gas: Helium at 150 kPa
• Injector temperature: 50 °C; column temperature: 50 °C
• Injection time: 40 ms (up to 150–200 ms for enhanced sensitivity)
• Sampling time: 30 s; total run time: 60 s
• Sample types: low concentration standard (96.8 ppm NH₃), high concentration standard (20.2% NH₃), and headspace ammonia solution (~10% NH₃ with water vapor)

Main Results and Discussion

Key performance metrics from ten replicate injections:

• Low concentration (96.8 ppm): RT = 0.617 min (RSD 0.0034%), area = 0.0786 mV·s (RSD 0.696%)
• High concentration (20.2%): RT = 0.600 min (RSD 0.0070%), area = 279.3 mV·s (RSD 0.018%)
• Real sample (~10% NH₃, saturated water): RT = 0.605 min (RSD 0.0066%), area = 143.4 mV·s (RSD 0.262%)

Chromatograms show sharp, well-resolved ammonia peaks with resolution >4 from nitrogen. The system demonstrated complete inertness against aqueous ammonia corrosion over six months. Monthly quality checks on three parallel channels yielded peak area and RT RSDs below 1%. Water elutes cleanly but is not recommended for quantification by GC.

Benefits and Practical Applications

• High repeatability and precision across a wide concentration range
• Excellent chemical inertness for samples containing moisture
• Rapid analysis suitable for online process monitoring and QA/QC
• Minimal peak tailing enhances quantitation at low ppm levels

Future Trends and Potential Applications

The demonstrated approach can be extended to other volatile amines and corrosive gases by leveraging MPD deactivation technology. Integration into automated sampling systems will support real-time process control. Emerging micro-GC platforms may incorporate multi-channel detection for simultaneous analysis of additional light gases.

Conclusion

The Agilent 990 Micro GC with a CP-Volamine column delivers robust, repeatable ammonia analysis from low ppm to high percentage levels. Its inert flow path ensures long-term stability against moisture and corrosion, making it a powerful tool for industrial, environmental and research applications.

Reference

1. Luong J. et al. Polar volatile compounds. Agilent Technologies application note, publication number A01915, 2011.