Improved ion chromatography column for separation of ethylenediamine carbamate and fluoride, and carbonate and sulfate in drinking water

Importance of the Topic

Municipal water disinfection generates potentially harmful inorganic byproducts such as chlorite, chlorate, and bromate. Accurate trace-level determination of these anions in drinking water preserved with ethylenediamine (EDA) is crucial for regulatory compliance and public health monitoring. The challenge lies in resolving EDA-derived artifacts and low-level oxyhalides using ion chromatography.

Study Objectives and Overview

This application update evaluates the Thermo Scientific™ Dionex™ IonPac™ AS30 column for simultaneous separation and quantification of EDA carbamate, fluoride, carbonate, sulfate, disinfection byproduct anions (chlorite, chlorate, bromate), and bromide in EDA-preserved drinking water. The aim is to improve resolution of interfering artifacts and achieve low detection limits using a multistep KOH gradient.

Methodology and Instrumentation

Instrumentation:

• Thermo Scientific Dionex Integrion HPIC RFIC system with KOH eluent generator, pump, degasser, suppressed conductivity detector (ADRS 600), and temperature-controlled column oven.
• IonPac AG30 Guard (2 × 50 mm) and IonPac AS30 analytical column (2 × 250 mm).
• Dionex AS-AP autosampler and buffer line for automated injection.

Reagents and Standards:

• Eluent: KOH gradient (1–66 mM) generated in situ.
• Stock solutions (1000 mg/L) of fluoride, bromide, chlorite, bromate, chlorate, phosphate, nitrate, DCA surrogate.
• Sample preservation: 50 mg/L EDA and 1 mg/L DCA added post-filtration.

Sample Preparation:
Filter samples through 0.45 µm membranes, discard initial filtrate, add EDA preservative and DCA standard.

Results and Discussion

Separation Performance:

• Baseline resolution of EDA carbamate, fluoride, carbonate, sulfate, chlorite, bromate, chlorate, bromide, and DCA achieved with a multistep KOH gradient.
• AS30 column outperforms AS27 and AS19 columns in resolving EDA artifacts and early-eluting analytes.

Analytical Figures of Merit:

• Linearity (r² ≥ 0.9995) across calibration ranges: chlorite (1–100 µg/L), bromate (1.25–30 µg/L), and common anions (10–500 µg/L).
• Method detection limits: chlorite 0.15 µg/L, bromate 0.29 µg/L, bromide 0.58 µg/L, and chlorate 0.60 µg/L.
• Precision: peak area RSD ≤ 1.2%; retention time RSD ≤ 0.02%.
• Recovery in spiked samples: 76–117% for oxyhalides and bromide; 97–103% for DCA surrogate.

Limitation:
High ionic strength waters (100 mg/L chloride) may overload the AS30 column, affecting bromate detection; dilution to half ionic strength is recommended.

Benefits and Practical Applications

The AS30 column with RFIC simplifies eluent preparation and enhances reproducibility. It supports reliable trace analysis of regulated oxyhalides and bromide in drinking water for compliance with EPA, WHO, and other guidelines.

Future Trends and Potential Applications

Integration of automated reagent-free IC systems for high-throughput water monitoring, expansion to emerging anionic contaminants, and coupling with mass spectrometric detection to improve selectivity and sensitivity.

Conclusion

The Dionex IonPac AS30 column combined with an electrolytic KOH gradient provides superior separation, low detection limits, and robust performance for the analysis of EDA-preserved drinking water samples. This method addresses key analytical challenges in monitoring disinfection byproducts and supports regulatory and health-based water quality assessments.

References

1. U.S. Environmental Protection Agency. Drinking Water Treatment; Document No. 810-F-99-013; 1999.
2. World Health Organization. Disinfectants and Disinfection By-Products; Environmental Health Criteria 216; 2000.
3. Kemsley, J. Bromate in Los Angeles Water. Chemical & Engineering News 85(52), 2007, 9.
4. World Health Organization. Bromate in Drinking Water. Background Document for WHO Guidelines; 2005.
5. U.S. EPA. National Primary Drinking Water Regulations: Disinfectants and Disinfection By-Products. Fed. Regist. 63(241), 1998, 69389–69476.
6. European Parliament and Council Directive 98/83/EC; 1998.
7. Japanese Ministry of Health, Labour and Welfare Directive No. 101; 2002.
8. Thermo Fisher Scientific. Application Update 198: Improved Determination of Trace Concentrations of Oxyhalides and Bromide in Drinking Water Using a Hydroxide-Selective Column; 2019.
9. Thermo Fisher Scientific. Application Note 167: Determination of Trace Concentrations of Oxyhalides and Bromide in Municipal and Bottled Waters Using RFIC; 2019.
10. U.S. EPA. EPA Method 300.1 Revision 1.0: Determination of Inorganic Anions in Drinking Water by Ion Chromatography; 2015.