Alkanolamine determinations in neutralizing amines samples with improved separation technology

Significance of the Topic

Neutralizing amine solutions are widely used in natural gas sweetening to remove CO2 and H2S impurities. Precise monitoring of alkanolamines and associated cationic impurities is critical to maintain process efficiency, prevent corrosion, and reduce operational costs.

Study Objectives and Overview

This work describes a novel ion chromatography (IC) method employing the Thermo Scientific Dionex IonPac CS20 column for simultaneous quantitation of six alkanolamines (ethanolamine, diethanolamine, triethanolamine, methyldiethanolamine, methylaminoethanolamine, dimethylaminoethanolamine) and four cations (sodium, ammonium, magnesium, calcium) in neutralizing amine samples. The goal was to achieve robust separation, low detection limits, and reliable performance in highly concentrated matrices.

Methodology and Instrumentation

Samples were diluted 1000-fold and injected via a 0.4 µL internal loop into a Dionex Integrion RFIC system with an AS-AP autosampler. Electrolytically generated methanesulfonic acid gradient elution (2.5–60 mM) was employed at 0.30 mL/min on a CS20 analytical column (2 × 250 mm) with CG20 guard (2 × 50 mm) at 35 °C. A CDRS 600 suppressor in recycle mode provided suppressed conductivity detection. Chromeleon CDS v7.2 managed data acquisition and processing.

• Instrument: Dionex Integrion HPIC with RFIC and AS-AP autosampler
• Columns: IonPac CS20 (2 × 250 mm) with CG20 guard (2 × 50 mm)
• Suppression: Dionex CDRS 600, 2 mm, 68 mA
• Eluent Generation: EGC 500 MSA cartridge, CR-CTC 600 trap column, HP degasser
• Detection: Suppressed conductivity
• Software: Chromeleon CDS 7.2

Key Results and Discussion

Baseline separation was achieved within 35 minutes for all target analytes, except near-baseline resolution for TEA and MDEA. Calibration curves fitted quadratically over 0.5–25 mg/L (cations and low-level amines) and 50–1250 mg/L (high-level amines) exhibited R2 > 0.99. Method detection limits ranged from 2 to 160 µg/L. Over five days of continuous operation, retention time RSDs were <0.5% and peak area RSDs <2.5%. Recovery studies in real EA-, TEA-, and MDEA-based samples yielded 90–110% recoveries.

Method Benefits and Practical Applications

The optimized CS20-based RFIC approach offers enhanced selectivity for monovalent and divalent ions, reduces sample preparation time, and minimizes column overload. This method supports quality control in gas sweetening operations, enabling timely adjustments of amine concentrations and corrosivity monitoring.

Future Trends and Potential Applications

Advances may include integration with mass spectrometry for structural confirmation, further miniaturization for field-deployable IC systems, and development of multi-dimensional separations to track amine degradation products in real time. Automation and process analytical technology (PAT) integration will streamline monitoring in industrial settings.

Conclusion

The described RFIC method using the IonPac CS20 column reliably quantifies key alkanolamines and cationic impurities in neutralizing amine solutions with high sensitivity, precision, and throughput, supporting efficient natural gas treatment processes.

References

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6. Thermo Scientific. Product Specification: Dionex IonPac CS20 Column, 2018.
7. ASTM D5127, Standard Practice for Reporting Results of Ion Chromatographic Analyses, 2013.
8. Thermo Scientific. Chromeleon CDS Software v7.2 User Manual.