Advances in Capillary Ion Chromatography Systems Using On-Line Electrolytic Eluent Generation and Suppressed Conductivity Detection

Significance of the Topic

The development of capillary ion chromatography (IC) addresses critical demands in modern analytical chemistry by offering enhanced mass sensitivity, higher separation efficiency, reduced eluent and sample consumption, and improved compatibility with mass spectrometry. These advances enable reliable trace-level detection of ionic analytes in complex or volume-limited samples, with continuous operation and rapid readiness for analysis.

Objectives and Study Overview

This study presents the design, implementation, and performance evaluation of the Thermo Scientific Dionex ICS-5000 capillary Reagent-Free IC (RFIC) system. Key aims include:

• Integration of on-line electrolytic eluent generation for KOH or MSA eluents.
• Deployment of post-column electrolytic suppression with suppressed conductivity detection.
• Support for both conventional (4 mm i.d.) and capillary (0.4 mm i.d.) separations in a single modular platform.

Methodology and Instrumentation

The core ICS-5000 system comprises three interchangeable modules—a dual-pump (DP) module, an eluent generator (EG) module, and a detector/chromatography (DC) module—together with the compact IC Cube housing capillary cartridges. The capillary configuration uses:

• A high-pressure non-metallic pump delivering deionized water at 10 µL/min.
• An electrolytic eluent generator cartridge producing precise KOH or MSA gradients under controlled current.
• A miniaturized degasser, sample injector, capillary separation column (IonPac AS19 or CS16), and electrolytic suppressor coupled to a suppressed conductivity detector.
• Chromeleon chromatography data system for system control and data acquisition.

Main Results and Discussion

Reproducibility and sensitivity tests demonstrate capillary RFIC performance on par with conventional systems:

• Isocratic separation of common anions on 0.4 mm × 25 cm AS19 columns achieved retention time RSDs of 0.06–0.09% and area RSDs of 0.24–0.50% (n = 30).
• Gradient separation of 22 anions showed retention time RSDs of 0.09–0.18% at 10 µL/min.
• Cation separation on CS16 columns delivered retention time RSDs of 0.05–0.09% and area RSDs of 0.30–0.46%.
• Capillary RFIC matched conventional ICS-2000 results in treated wastewater analysis for major anions.
• Trace analysis via large-volume injection (10 µL) enabled detection of anions at 0.2–1.0 µg/L with excellent signal-to-noise ratios.
• Two-dimensional IC (2D-IC) coupling conventional (4 mm) and capillary (0.4 mm) columns enhanced bromate detection down to low ng/L levels in drinking water.
• Fast separations of seven anions and six cations were completed in under 5–6 minutes at elevated flow rates up to 20 µL/min.

Benefits and Practical Applications

Capillary RFIC systems offer multiple practical advantages:

• Reduced eluent and water consumption by over 99% compared to conventional IC.
• Continuous, reagent-free operation with minimal manual preparation.
• High-throughput trace analysis for environmental, pharmaceutical, and quality-control laboratories.
• Seamless integration with mass spectrometry and on-line sample concentration.
• Modular flexibility to configure single or dual-channel, conventional or capillary, and 2D-IC workflows.

Future Trends and Applications

Emerging developments are poised to further expand capillary IC capabilities:

• New capillary stationary phases for challenging selectivity and chiral separations.
• Smaller, fully integrated systems for field-deployable and point-of-use analysis.
• Enhanced multi-dimensional separations (3D-IC) and on-line sample preparation modules.
• Tighter coupling with high-resolution mass spectrometry for structural elucidation.
• Artificial intelligence-driven method development and real-time data correction.

Conclusion

The Thermo Scientific Dionex ICS-5000 capillary RFIC platform successfully combines on-line electrolytic eluent generation, robust suppressor technology, and suppressed conductivity detection to deliver fast, reproducible, and sensitive separations. Its modularity supports both conventional and capillary workflows, enabling versatile applications in trace ionic analysis across diverse industries.