Amines and ammonia - Analysis of impurities in amine streams

Importance of the Topic

Amines and ammonia are critical components in many industrial processes, including gas sweetening and chemical synthesis. Accurate detection of trace polar impurities in amine streams ensures product quality, process safety, and regulatory compliance. Reliable separation and quantification of low-molecular-weight amines, water, and ammonia support effective monitoring and optimization of purification operations.

Objectives and Overview

This application note evaluates a gas chromatography (GC) method using a highly inert capillary column to separate and quantify ammonia, water, and volatile amines in process streams. The goal is to demonstrate rapid, reproducible analysis of methanol, ethanol, mono-, di-, and trimethylamines alongside interfering matrix components.

Methodology and Instrumentation

The analysis employs capillary GC with a thermal conductivity detector (TCD) under the following conditions:

• Column: Agilent CP-Volamine, 0.32 mm × 60 m fused silica (df optimized), part no. CP7448
• Temperature program: 40 °C (10 min), ramp to 250 °C at 20 °C/min
• Carrier gas: Helium at ~68 kPa
• Injection: Split 1:50, sample volume 0.5 µL
• Detector: Thermal conductivity (TCD)

Main Results and Discussion

The CP-Volamine column achieves sharp, baseline separation of ammonia, water, and seven common volatile amines and solvents. Observed retention order and approximate concentration ranges are:

1. Ammonia (12 %)
2. Water (33 %)
3. Monomethylamine (2.5 %)
4. Diethyl ether (7 %)
5. Methanol (10 %)
6. Dimethylamine (3 %)
7. Trimethylamine (31 %)

The inert column surface prevents peak tailing and allows reliable quantification of polar analytes even in high-water matrices. Reproducibility studies show consistent retention times and peak shapes across multiple injections.

Benefits and Practical Applications

• High selectivity for polar impurities without derivatization
• Rapid analysis with a 10 min hold and 20 °C/min ramp
• Robust performance in moisture-rich samples
• Applicable to QA/QC of gas sweetening, amine recycling, and environmental monitoring

Future Trends and Opportunities

Emerging developments include integration of mass spectrometric detection for enhanced sensitivity and specificity, miniaturized GC systems for field diagnostics, and automated sample preparation modules. Further column chemistry advances may extend applicability to larger amines and related polar species.

Conclusion

The described GC-TCD method using the CP-Volamine column provides a reliable, high-throughput approach for comprehensive profiling of ammonia, water, and volatile amines in industrial streams. Its robust performance and straightforward operation make it well suited for routine process control and research applications.

References

Agilent Technologies, Inc. Amines and ammonia: Analysis of impurities in amine streams. Application Note A01994, 2011.