Cost-Effective Determination of Inorganic Anions and Cations in Municipal Drinking Water Using Capillary Ion Chromatography

Importance of the Topic

The accurate measurement of common inorganic anions and cations in municipal drinking water is essential to ensure compliance with regulatory standards and to protect public health. Elevated levels of fluoride, nitrite, nitrate, sodium, ammonium and other ions can pose significant health risks and affect aesthetic water quality.

Objectives and Study Overview

This application brief evaluates the performance of a capillary ion chromatography system for simultaneous determination of inorganic anions and cations in undiluted municipal drinking water. Key goals included reducing reagent consumption, minimizing system downtime, and demonstrating reliable quantification within regulatory limits.

Methodology and Used Instrumentation

The analysis was conducted using a Thermo Scientific Dionex ICS-5000 capillary IC system equipped with an AS-AP autosampler and Chromeleon data software. Reagent-Free IC with eluent generation (RFIC-EG) provided potassium hydroxide for anion separation and methanesulfonic acid for cation separation. Sample injection volume was 0.4 microliter at a flow rate of 10 microliter per minute. Columns and conditions employed:

• Anion analysis on Dionex IonPac AG19 guard and AS19 analytical capillary columns, gradient 15 to 60 mM KOH over 18 minutes, column temperature 30 °C, suppressed conductivity detection
• Cation analysis on Dionex IonPac CG12A guard and CS12A analytical capillary columns, gradient 6 to 65 mM MSA over 30 minutes, column temperature 40 °C, suppressed conductivity detection

Main Results and Discussion

All target anions (chloride, nitrate, sulfate, fluoride) were separated in under 13 minutes, and cations (sodium, ammonium, potassium, magnesium, calcium) in under 12 minutes. Precision was excellent, with relative standard deviation of peak areas at 0.6 percent over 60 injections in 24 hours. The capillary RFIC-EG system consumed less than 15 mL of source water per day, allowing continuous operation with a stable baseline and fewer calibrations. Eluent cartridge life extended to 18 months, greatly reducing waste and ownership cost.

Benefits and Practical Applications

This capillary IC approach offers multiple advantages for routine water quality monitoring:

• Low reagent and waste generation
• High mass sensitivity for trace-level detection
• Rapid analysis turnaround with minimal equilibration time
• Continuous on-line readiness to streamline laboratory workflow
• Reliable compliance testing for drinking water and process or wastewater streams

Future Trends and Potential Applications

Advancements in capillary IC are expected to focus on further miniaturization, integration with mass spectrometric detection, and development of multi-ion methods for broader analyte coverage. Automated sampling and remote operation will support real-time water quality surveillance in municipal distribution systems and industrial effluents.

Conclusion

The capillary Thermo Scientific Dionex RFIC-EG system delivers a cost-effective, high-throughput solution for determination of inorganic anions and cations in drinking water. Its low eluent consumption, robust performance and ease of use make it an ideal platform for routine environmental and industrial water analysis.

References

1. US Environmental Protection Agency Method 300.0 Rev 2.1, 1993
2. Greenberg AE Clesceri LS Eaton AD Eds Standard Methods for the Examination of Water and Wastewater 18th ed APHA 1992
3. ASTM D4327-97 Standard Test Methods for Anions in Water by Chemically Suppressed Ion Chromatography 1999
4. Dionex Corporation Technical Note 90 LPN 2649 2011