Metrosep C 6 (Column manual)

Significance of the topic

Ion chromatography using high-capacity cation exchange columns plays a central role in environmental analysis, pharmaceutical quality control and industrial process monitoring. Reliable separation of common cations, low-level amines and transition metals allows laboratories to meet stringent regulatory and research requirements with robust, reproducible methods.

Objectives and overview of the manual

This manual for the Metrosep C 6 series (2 mm and 4 mm ID) provides a complete guide from ordering through application examples and troubleshooting. It aims to enable analysts to select the correct column version, prepare eluents, perform instrument start-up and achieve optimal separations across a broad range of analytes and sample matrices.

Methodology and instrumentation

The Metrosep C 6 columns are silica-based, carboxylated exchange phases with a 5 µm particle size, operated over pH 2–7 (eluent) and 2–10 (sample) at 20–60 °C. PEEK iColumn housings store chip-based metadata. Key system components include:

• High-pressure pump with flow control (0.25–0.9 mL/min recommended)
• Inline degasser or vacuum degassing for bubble-free eluents
• 0.45 µm eluent filters and guard columns to remove particles and contaminants
• Conductivity detector, with or without chemical suppression
• Optional Inline Sample Preparation (MISP) modules for cleanup or dilution

Instrumentation

• Metrohm Ion Chromatograph with PEEK Smart iColumn interface
• High-capacity Metrosep C 6 columns (100, 150, 250 mm lengths; 2 mm and 4 mm IDs)
• Guard columns matching the separation phase
• Pulsation absorber to protect delicate packing

Main findings and discussion

System conditioning and eluent quality critically affect baseline stability and reproducibility. Varying nitric acid (2–7 mmol/L), dipicolinic acid (0–5 mmol/L), oxalic acid and organic modifiers (acetone, acetonitrile up to 30 %) demonstrates tunable retention for mono- and divalent cations, amines and transition metals. Temperature (20–60 °C) and flow rate (up to 3.5 mL/min) influence resolution and analysis time. Under optimized conditions, Na/NH4 separation tolerates >70 000:1 concentration ratios. Real-world applications include cation profiling in beer, infusion solutions, snow and industrial electrolytes.

Benefits and practical applications

• Wide selectivity for common inorganic and organic cations
• High sample throughput via fast gradients on 2 mm microbore or 4 mm preparative columns
• Robustness against bacterial growth and matrix effects through guard columns and inline filters
• Flexible method optimization by adjusting eluent composition, temperature and flow
• Real-time system metadata recording via Smart iColumn chip

Future trends and possibilities

Ongoing developments include automated Inline Sample Preparation for trace-level analysis, hyphenation with mass spectrometry for enhanced specificity, microfluidic column formats for ultra-fast screening, and AI-driven diagnostics to predict maintenance needs. Emerging eluent chemistries and greener solvents will further expand the technique’s eco-friendly profile.

Conclusion

The Metrosep C 6 series offers a versatile platform for reliable cation and amine separations across research, QA/QC and industrial settings. Comprehensive guidance on column selection, eluent preparation, system start-up, and troubleshooting ensures reproducible, high-resolution results and long column lifetime.

References

• Metrohm AG. Metrosep C 6 Column Manual, Version 8.107.8050EN, 2022.
• Application Note C-142: Standard cation separation on Metrosep C 6 columns, Metrohm.
• Application Note C-144: Variable Inline Preconcentration with matrix elimination, Metrohm.
• Application Note C-154: Fast IC of cations in drinking water with high-capacity columns, Metrohm.
• Ismail L. et al., Toward understanding reactive species in photocatalytic degradation, Appl. Catal. B, 185, 2016.
• De Vrieze J. et al., High salinity shifts anaerobic digestion to carboxylate production, Water Res., 98, 2016.