Practical guidance for using capillary anion chromatography

Significance of the topic

Capillary ion chromatography uses 0.4 mm columns and low flow rates (10–30 µL/min) to enhance mass sensitivity, reduce solvent consumption (~5 L per year), and minimize waste. This approach is particularly valuable for trace analysis and samples of limited volume.

Objectives and overview

This technical note provides best practices for the installation and operation of the Thermo Scientific Dionex ICS-5000 capillary IC system. It compares capillary and standard bore IC formats and presents methods for direct injection, large-loop injection, and monolith concentrator-based preconcentration of trace anions.

Instrumentation

• Thermo Scientific Dionex ICS-5000 capillary IC system: SP/DP pump, EG eluent generator, IC Cube module, CD conductivity detector, degas cartridge.
• Thermo Scientific Dionex AS-AP autosampler.
• Capillary cartridges and columns: EGC-KOH, CR-ATC, ACES 300 suppressor, CRD 200 carbonate removal device.
• IonSwift Monolith Anion Concentrator (MAC-100) columns.
• Dionex ICW-3000 Online Water Purifier for ultrapure water supply.
• Thermo Scientific Chromeleon CDS for data acquisition.

Methodology

• Minimize dead volume and air entrapment by using precision-cut PEEK tubing, blue connectors, and ferrules; install and prime each connection sequentially while preventing gaps and bubbles.
• Maintain continuous system operation to ensure stable flow rates; relieve pressure before shutdown to avoid water ingress into columns and suppressors.
• Prepare the autosampler by flushing the flow path, aligning the needle and tray, and calibrating transfer line volume according to the operator’s manual.
• Perform direct injections using small loops (0.4–10 µL) in push or pull modes; calibrate with multiple standards to establish linear response.
• For large-volume preconcentration, install a capillary monolith concentrator column (MAC-100) in the autosampler valve, condition it, and use partial-loop injections with controlled syringe speeds to load up to 800 µL with high reproducibility.

Main results and discussion

• Simultaneous injections on 2 mm microbore (10 µL loop, 0.25 mL/min) and 0.4 mm capillary (0.4 µL loop, 10 µL/min) columns produced comparable peak responses for a nine-anion standard, confirming mass-sensitivity scaling with the square of column radius.
• Direct large-loop injection of a 1:100 000 diluted standard using a 10 µL loop on capillary columns achieved µg/L detection limits for common anions within a 20 min run.
• Concentration mode with a 200 µL injection onto a MAC-100 concentrator column and elution at 12 µL/min enabled detection of trace anions at 11–24 ng/L, replicating the sensitivity of a 5 mL injection on standard systems when using inline purified water.

Benefits and practical applications of the method

1. Enhanced mass sensitivity enables analysis of limited or dilute samples with sub-µL injections.
2. Substantial reductions in water and eluent consumption lower costs and environmental footprint.
3. Streamlined large-volume injections without auxiliary pumps simplify sample handling.
4. Continuous operation design ensures rapid readiness and minimal equilibration times.

Future trends and applications

• Expansion in pharmaceutical, environmental, and semiconductor sectors for ultratrace ion monitoring.
• Integration of inline water purification and advanced monolith materials for broader ion selectivity.
• Automation improvements for unattended, high-throughput quality control and research workflows.

Conclusion

Capillary IC offers chromatographic performance on par with conventional systems while delivering superior sensitivity, lower solvent usage, and simplified sample handling. Adherence to precise plumbing protocols and use of monolith concentrators enable reliable trace anion detection down to ng/L levels.

References

1. Thermo Fisher Scientific. Dionex ICS-5000 Ion Chromatography Operator’s Manual. Document No. 065342; 2011.
2. Christison T, Madden J, Pang F, Divan K. Walk-Up High-Pressure Capillary Ion Chromatograph for Fast Separation of Pharmaceutical Inorganic Ions. LPN 2967; 2011.
3. Thermo Fisher Scientific. Dionex ICS-5000 Ion Chromatography System Installation Instructions. Document No. 065343; 2011.
4. Thermo Fisher Scientific. Dionex ICS Series AS-AP Autosampler Operator’s Manual. Document No. 065361; 2011.
5. Thermo Fisher Scientific. Technical Note 112: Determination of Trace Ions in Ultrapure Water Using Capillary Ion Chromatography. LPN 3041; 2011.
6. Thermo Fisher Scientific. Product Manual for Dionex IonSwift Monolith Anion Concentrator (MAC). Document No. 065387; 2010.
7. Thermo Fisher Scientific. Technical Note 90: Mass Sensitivity of Capillary IC Systems Explained. LPN 2649; 2011.