Water analysis: The role of standardized ion chromatography

Importance of the Topic

Ion chromatography has become a cornerstone technique in water quality monitoring due to its high selectivity, sensitivity, and capacity to separate a wide range of inorganic and organic ions. The accurate measurement of anions and cations—including nutrient ions (nitrate, phosphate), common electrolytes (chloride, sulfate), regulated toxic species (bromate, perchlorate, hexavalent chromium), and emerging contaminants (polar pesticides, disinfection by-products)—is essential for public health, environmental protection, and compliance with regulatory standards worldwide.

This white paper reviews internationally recognized ISO and ASTM methods, highlights best practices for sample preparation and detection, and illustrates how modern ion chromatography systems meet the demanding requirements of drinking water, surface water, and wastewater analysis.

Objectives and Study Overview

This document aims to provide a clear, practical overview of standardized ion chromatography workflows for water analysis. It examines:

• Key ISO and ASTM standards for anion and cation determination
• Methodological options: isocratic versus gradient elution
• Detection modes: suppressed and non-suppressed conductivity, UV/VIS, and mass spectrometry
• Sample preparation strategies including inline matrix elimination and solid-phase extraction
• Examples of routine and trace analyses for regulated and unregulated analytes

Methodology

Standardized workflows rely on high-purity reagents (Type 1 DI water), calibrated reference standards, and well-defined chromatographic parameters. Two main detection modes are applied:

• Suppressed conductivity: provides low background, high sensitivity, and compatibility with gradient elution
• Non-suppressed conductivity: simpler setup for isocratic cation analysis where high ionic strength matrices do not require suppression

Eluents are generated either manually (carbonate/hydrogen carbonate or methanesulfonic acid) or reagent-free via electrolytic generators (KOH or NaOH). Sample preparation may include pH adjustment, filtration (0.2 µm), inline guard cartridges (Ag, Ba, H), and offline SPE for trace analyte preconcentration.

Used Instrumentation

• Thermo Scientific Dionex ICS-5000+ and ICS-6000 IC Systems
• Thermo Scientific Dionex IonPac™ analytical and guard columns (AS7, AS23, AS19, CS12A, CS16)
• Continuously regenerated suppressors (AERS, CERS, AMMS) for conductivity detection
• Thermo Scientific Dionex Chromeleon™ CDS for automated calibration and system suitability testing
• Electrolytic eluent generators (EGC KOH, EGC NaOH cartridges)
• Thermo Scientific Dionex OnGuard™ pre-treatment cartridges (Ag, Ba, H)
• UV/VIS detectors and post-column derivatization modules for chromate and bromate
• ESI-MS/MS interface for trace perchlorate analysis

Main Results and Discussion

Comparative evaluations demonstrate that suppressed conductivity detection with high-capacity columns efficiently separates common anions in under five minutes under isocratic conditions (e.g., AS22-Fast-4µm). Gradient KOH elution on AS18 or AS19-4µm extends the working range for complex wastewaters and oxyhalides while maintaining low baseline drift.

Cation analysis using CS12A or CS16-4µm columns and methanesulfonic acid eluents achieves baseline resolution of alkali and alkaline earth metals, with suppressed detection offering enhanced sensitivity for trace ammonium and lithium.

Trace determinations of bromate, chlorate, chlorite, and perchlorate comply with ISO 15061/D6581, ISO 11206, ISO 19340, and EPA Method 332.0. Inline SPE and matrix elimination cartridges effectively reduce high chloride and sulfate loads, enabling sub-µg/L quantification. Post-column derivatization using 1,5-diphenylcarbazide or iodide reagents expands selectivity for hexavalent chromium and bromate.

Benefits and Practical Applications

• Universal workflows for drinking water, wastewater, and surface water matrices
• Regulatory compliance with ISO, ASTM, U.S. EPA, and EU directives
• Flexible detection: conductivity, UV, VIS, and MS/MS for multi-residue analysis
• Rapid runtime and high throughput using high-efficiency columns and automated CDS control
• Robust quality control: system suitability tests, inline eluent generation, and traceability

Future Trends and Potential Uses

Future developments include deeper integration of IC with high-resolution mass spectrometry for non-target screening of polar micropollutants, automated inline sample cleanup for diverse matrices, and miniaturized IC systems for field-deployable monitoring. Advances in column chemistries and suppression technologies will further shorten runtimes and enhance peak capacity.

Conclusion

Standardized ion chromatography methods form an essential framework for reliable water analysis. By combining modern reagent-free eluent generation, advanced suppressors, and software-driven automation, laboratories can meet stringent regulatory requirements, achieve low detection limits, and handle diverse water matrices with confidence.

Reference

1. ISO 10304-1:2007 Water quality—Dissolved anions by liquid chromatography
2. ISO 14911:1998 Water quality—Dissolved cations by ion chromatography
3. ISO 15061:2001 Determination of dissolved bromate by ion chromatography
4. ISO 19340:2017 Determination of dissolved perchlorate by ion chromatography
5. ASTM D4327-17 Anions in water by suppressed ion chromatography
6. ASTM D6919-17 Alkali and alkaline earth cations and ammonium by ion chromatography
7. ASTM D5257-17 Dissolved hexavalent chromium in water by ion chromatography
8. U.S. EPA Method 332.0 Perchlorate in drinking water by IC-ESI-MS