BASICS OF ION CHROMATOGRAPHY

Importance of the Topic

High‐performance ion chromatography (HPIC) is a cornerstone technique for trace analysis of ionic species in environmental, industrial, and life‐science applications. Its combination of high selectivity, sensitivity, and throughput makes it ideal for monitoring water quality, process streams, and complex matrices in power generation, semiconductor fabrication, food and beverage testing, and consumer products.

Goals and Article Overview

This white paper by Dr. Joachim Weiss (Thermo Fisher Scientific) reviews the fundamental mechanisms, stationary phases, eluent systems, detection modes, and major applications of modern liquid‐phase ion chromatography. It covers:

• Separation modes: ion exchange, ion‐exclusion, and ion‐pair chromatography
• Stationary‐phase design: nanobead‐agglomerated, grafted polymers, hyperbranched condensates, monoliths, mixed‐mode
• Eluent generation: carbonate, hydroxide (RFIC), and specialized buffers
• Detection methods: suppressed conductivity (chemical/electrolytic), pulsed amperometry, spectrophotometric, fluorescence, charged aerosol, and hyphenated IC–MS/ICP techniques
• Applications spanning water analysis, power‐plant chemistry, semiconductors, detergents, food/beverages, pharmaceuticals, and environmental monitoring

Methods and Instrumentation Used

• Separator columns: surface‐sulfonated or surface‐aminated polystyrene/divinylbenzene (PS/DVB), grafted PS/DVB, hyperbranched polymers, polymer and silica monoliths, mixed‐mode NSH phases
• Eluent generation and suppression: Reagent‐Free IC eluent generators for KOH, EPM pH modifiers, continuously‐regenerated membrane suppressors (DRS 600, CRS 500), capillary suppressors (ACES 300)
• Detection modules: conductivity cells, gold/palladium/carbon electrodes for pulsed/integrated amperometry, UV/visible absorption cells, fluorescence detectors with postcolumn derivatization mixers, charged aerosol detectors (CAD)
• Hyphenated interfaces: ESI interfaces for IC–MS(/MS), nebulization systems for IC–ICP–MS/ OES
• Autosampler and valve configurations for preconcentration and matrix elimination: 6-port/10-port valves, concentrator/trap columns, AutoPrep (EWP) modules

Main Results and Discussion

The paper demonstrates how advances in stationary‐phase chemistry and eluent generation have expanded ion chromatography from its origins in inorganic‐anion analysis to a universal tool for ions up to large biomolecules. Key achievements include:

• High‐capacity, hydroxide‐selective resins enabling fast gradient separation of inorganic/organic anions and neutral organics
• Hyperbranched condensate resins with narrow selectivity for polarizable species (perchlorate, cyanide, nitrite) and trace disinfection byproducts (bromate, haloacetic acids)
• Surface‐aminated monoliths and tentacular phases delivering high resolution of proteins, antibodies, and nucleotides
• On‐line eluent generation and suppression yielding stable, high‐purity mobile phases for RFIC
• Coupling to MS/ICP for speciation analysis (Cr(III)/Cr(VI), arsenic species, trace metals, iodine in milk and seawater)
• Mixed‐mode columns facilitating simultaneous separation of neutral organics, anions, and cations in pharmaceuticals, detergents, and cosmetics

Benefits and Practical Applications

Ion chromatography offers critical benefits across industries:

• Drinking and ultrapure water monitoring: multi‐anion/cation profiles, trace perchlorate, bromate and bromide, fluoride, polysilicates, boron
• Power plants: steam‐cycle corrosion monitoring (chloride, sulfate, acetate, ammonia), flue‐gas scrubber oxoanions, polythionates, amines
• Semiconductors: ultra‐trace detection of metal ions, acids/bases in etchants, cleaning solvents, process water
• Detergents/home care: surfactant speciation, builder analysis (phosphates, EDTA), peroxide/activator chemistry
• Food and beverage: organic acids, carbohydrates, anions in juices, wines, beer; nitrate/nitrite in meats; trace iodine in milk
• Pharmaceuticals: counter‐ion/drug profiling, antibody charge variants by pH‐gradient chromatography

Future Trends and Possibilities

Emerging directions include:

• Further miniaturization: capillary and micro‐IC for low‐volume, high‐sensitivity analyses
• Automated, on‐line preconcentration and sample prep leveraging EWP modules
• Integration with high‐resolution MS(/MS) for comprehensive speciation and non‐target screening
• Advanced mixed‐mode phases for challenging matrices and coeluting ionic/neutral analytes
• Enhanced bioanalytical applications: glycan, peptide, and nucleotide mapping workflows
• Green IC: lower solvent consumption, sustainable eluent generation

Conclusion

Over four decades, ion chromatography has evolved into a universal separation platform for ionic and ionizable compounds across diverse sectors. Continued innovations in stationary‐phase design, eluent generation, suppression, and detection have unlocked high‐speed, high‐sensitivity analyses from inorganic ions through small organics to large biomolecules. Whether for environmental compliance, process control, or life‐science research, modern IC delivers the selectivity, robustness, and automatability required to meet future analytical challenges.

References

1. H. Small, T. Stevens, W. Bauman, Anal. Chem. 47 (1975) 1801–1809
2. P. Šenkýř, T. Vegl, J. Chromatogr. A 1436 (2016) 108–119
3. A. Seidel‐Morgenstern, F. Schmidt, Separation Science and Technology 55 (2020) 23–44
… (complete reference list available in original eBook)