New Developments in Capillary Ion Chromatography Systems Using On-Line Electrolytic Eluent Generation

Significance of the Topic

Capillary ion chromatography reduces sample and eluent consumption while enhancing mass sensitivity, separation efficiency, and analysis speed. Continuous operation and low flow rates facilitate coupling with mass spectrometry and enable trace-level determinations in volume-limited or matrix-rich samples.

Objectives and Study Overview

This white paper presents the design and performance evaluation of the Thermo Scientific Dionex ICS-5000 Capillary Reagent-Free IC system. Goals include implementing on-line electrolytic eluent generation for KOH or MSA, demonstrating suppressed conductivity and pulsed amperometric detection modes, and validating analytical capabilities for anions, cations, and carbohydrates in challenging matrices.

Instrumentation

• System modules: Dual-Pump, Eluent Generator, Detector/Chromatography and the IC Cube™ capillary cartridge housing degasser, injection valve, column, suppressor, and optional carbonate removal device.
• Eluent generation: On-line electrolytic production of eluents from deionized water at capillary scale.
• Columns: 0.4 mm i.d. capillary columns—IonPac AS19, AS18, AS15 for anions; CS16, CS12A for cations; CarboPac PA20 for carbohydrates.
• Detectors: Suppressed conductivity with electrolytic capillary suppressors; pulsed amperometric detection using Au working electrode and PdH reference electrode.
• Operating conditions: Flow rates 10–20 µL/min, injection volumes 0.4–180 µL, column temperatures 30–40 °C.

Results and Discussion

• Anion separations achieved isocratic and gradient analysis of up to 22 species with retention time RSDs ≤ 0.18 % and peak area RSDs ≤ 0.50 %.
• Cation analyses of common alkali and alkaline earth ions yielded retention time RSDs ≤ 0.092 % and area RSDs ≤ 0.46 % over 30 injections.
• Trace anion detection down to 0.1 µg/L–1.0 µg/L with high signal-to-noise; capillary concentrator enabled loading up to 180 µL for low-level quantitation.
• Fast methods: Seven anions separated in < 5 min and six cations in < 6 min at flow rates up to 20 µL/min.
• Application examples: Treated wastewater anion profiling matched conventional IC performance; carbohydrate profiling in coffee and juices with pulsed amperometry demonstrated reproducible retention time RSDs ≤ 0.12 % and area RSDs ≤ 0.97 %.

Benefits and Practical Applications

Capillary RFIC with on-line eluent generation offers:

• Minimal reagent use and continuous operational readiness.
• Enhanced sensitivity for trace ions in small sample volumes.
• Improved selectivity and speed with capillary columns.
• Seamless mass spectrometry compatibility.
• Reduced maintenance and operational costs.

Future Trends and Applications

• Further miniaturization and integration with microfluidic sample prep.
• Expanded coupling with high-resolution mass spectrometry for speciation.
• Development of novel stationary phases for challenging analytes.
• High-throughput workflows in environmental, pharmaceutical, and food analysis.
• Enhanced automation and reliability in reagent-free systems.

Conclusion

The Dionex ICS-5000 capillary RFIC platform with on-line electrolytic eluent generation and advanced detection modes delivers robust, reproducible, and sensitive analysis of ionic and electroactive species. Its low consumption, high throughput, and broad application scope make it a versatile solution for modern analytical laboratories.