Alkyl amines in scrubber solutions

Importance of the Topic

Scrubber solutions containing alkyl amines play a critical role in industrial gas sweetening by neutralizing acidic gases such as H₂S and CO₂. Effective removal of these corrosive species protects equipment and piping in refineries, natural gas facilities, and chemical plants. Beyond corrosion control, mono-, di-, and triethanolamines as well as methylamines are valuable intermediates in detergent, emulsifier, pharmaceutical, and specialty chemical production. Precise monitoring of amine and cation concentrations in complex scrubber matrices is therefore essential for process safety, product quality, and operational efficiency.

Objectives and Study Overview

This application note demonstrates the development of an ion chromatography method for simultaneous determination of ethanolamines, methylamines, and common inorganic cations in scrubber solutions. The main goals were:

• Achieve clear separation of six amines (MEA, DEA, TEA, MMA, DMA, TMA) from alkali and alkaline earth cations.
• Optimize run time to under 25 minutes while maintaining resolution above 1.6.
• Establish a robust protocol suitable for both laboratory and on-line process monitoring.

Used Instrumentation

• IC System: 930 Compact IC Flex Oven/Deg with built-in degasser
• Detector: 2.850.9010 IC Conductivity Detector (non-suppressed)
• Column: Metrosep C 6 – 150/4.0 with Metrosep RP 2 Guard/3.5
• Autosampler: 858 Professional Sample Processor – Pump
• Software: MagIC Net 4.0 Professional

Methodology and Instrumentation

A mobile phase composed of nitric acid, dipicolinic acid, and acetone was optimized for non-suppressed conductivity detection at 30 °C. A 20 µL injection volume was employed. Method development involved systematic variation of column temperature, flow rate, and eluent modifiers to accelerate elution, sharpen peaks, and reorder divalent cation signals for better resolution.

Main Results and Discussion

The finalized method resolved all six amines from lithium, sodium, ammonium, potassium, magnesium, and calcium in under 25 minutes with resolution factors >1.6 for all analyte pairs and >3.1 for critical sodium / ammonium separation. The high-capacity Metrosep C 6 column tolerated larger injection volumes without peak broadening. Inline dilution and optional extension to a 250 mm column allow handling of higher analyte concentrations while preserving resolution.

Benefits and Practical Applications of the Method

• Direct, non-suppressed analysis simplifies system setup and maintenance.
• High precision and reproducibility ensure reliable process control.
• Flexibility for laboratory QC and on-line monitoring across multiple process points.
• Scalable injection volumes and column configurations adapt to varying sample matrices.

Future Trends and Potential Applications

Advances in automated sample preparation (dialysis, ultrafiltration), dynamic injection control (MiPT), and dual-detector setups (conductivity with mass spectrometry) will further enhance sensitivity, throughput, and compound confirmation. Suppressed conductivity analysis can extend quantification to trace-level cations while maintaining robust process analytics.

Conclusion

A non-suppressed ion chromatography method using a high-capacity Metrosep C 6 column and direct conductivity detection offers a rapid, precise, and adaptable solution for monitoring alkyl amines and inorganic cations in scrubber solutions. The approach supports both laboratory and online process applications, ensuring optimal amine dosing and corrosion protection in gas sweetening operations.