Efficient Separations Obtained by Using Smaller Particle Size Analytical Columns with a High-Pressure Ion Chromatography System

Importance of the topic

Ion chromatography is a key technique for anion and cation analysis in environmental, food and industrial matrices. High-efficiency separations and faster analysis times improve laboratory throughput and data quality, especially for complex samples requiring resolution of closely eluting species.

Objectives and study overview

This study evaluates the performance of 4 µm particle size analytical columns (AS11-HC, AS18, CS19) coupled to a modified Thermo Scientific Dionex ICS-5000 high-pressure IC system. The goal is to demonstrate enhanced separation efficiency, reduced run times, and higher sample throughput in municipal and mineral water, fruit juice and wine samples.

Methodology and instrumentation

• Instrument: Modified Dionex ICS-5000 HPIC system with prototype high-pressure pumps, eluent generator cartridges and degas modules supporting up to 5 000 psi.
• Columns: IonPac AS11-HC-4 µm (4×250 mm), AS18-4 µm (2×150 mm), CS19-4 µm (4×250 mm) with AutoSuppression™ external water mode suppressor.
• Eluents: Hydroxide gradient (1–60 mM KOH with 10–20 % methanol) for anions; 8 mM methanesulfonic acid for cations.
• Detection: Suppressed conductivity detection using ASRS or CSRS suppressors.
• Samples: Municipal and mineral water, orange juice, white wine; minimal sample preparation by dilution and filtration.

Main results and discussion

The 4 µm anion-exchange columns separated inorganic anions in municipal and mineral water in under 4 min and resolved over 30 organic and inorganic species in fruit juice and wine in single runs. Compared to conventional 9 µm columns, baseline resolution improved significantly (for example formate–butyrate resolution increased from 1.16 to 1.25). The CS19-4 µm cation column resolved six common cations in under 7 min at 1 mL/min flow rate. At high flow rates, backpressures up to 4 200 psi were managed without loss of peak efficiency.

Benefits and practical applications

• Enhanced resolution of closely eluting species (e.g. monovalent carboxylates, halides, phosphate/phthalate).
• Reduced analysis times (up to 50 % shorter runs) increasing sample throughput.
• Reliable peak integration and quantitation in complex matrices.
• Compatibility with existing Reagent-Free IC methods and simple sample preparation.

Future trends and opportunities

• Adoption of sub-2 µm particles for ultra-high-resolution separations.
• Expansion of high-pressure platforms for microbore and capillary columns (0.4–4 mm i.d.).
• Integration with mass spectrometry for trace-level target analysis.
• Applications in emerging fields such as metabolomics, pharmaceutical quality control and advanced environmental monitoring.

Conclusion

Coupling small-particle IonPac columns with a high-pressure IC system delivers superior separation performance and faster run times for both anions and cations. This combination enhances laboratory productivity and extends the applicability of IC to challenging complex matrices.

References

1. Thermo Fisher Scientific, Application Note 154: Determination of Inorganic Anions in Environmental Water Using a Hydroxide-Selective Column.
2. Thermo Fisher Scientific, Application Note 143: Determination of Organic Acids in Fruit Juices.
3. Thermo Fisher Scientific website: IonPac CS19 column product information.