Improved Determination of Trace Concentrations of Oxyhalides and Bromide in Drinking Water Using a Hydroxide-Selective Column

Significance of the Topic

Safe drinking water is critical to public health. Chemical disinfection processes generate oxyhalide byproducts such as chlorite, chlorate, and bromate that pose potential health risks at trace levels. Regulatory agencies worldwide set stringent maximum contaminant levels (MCLs), for example 10 μg/L for bromate in municipal water. Reliable, sensitive, and selective analytical methods are required to monitor these species in complex matrices and ensure compliance with guidelines.

Objectives and Study Overview

This study evaluates a high-capacity, hydroxide-selective ion‐exchange column (Thermo Scientific Dionex IonPac AS27) coupled with reagent‐free ion chromatography (RFIC) to improve the trace determination of oxyhalides and bromide in drinking water, especially in samples preserved with ethylenediamine (EDA). It compares performance against the AS19 column, focusing on resolution, detection limits, and applicability to real and high‐ionic‐strength waters.

Instrumentation Used

• Thermo Scientific Dionex ICS‐5000+ HPIC system with SP single pump, eluent generator, and detector/chromatography compartment
• Thermo Scientific Dionex AS‐AP autosampler with 1000 µL syringe and buffer line assembly
• Dionex EGC 500 potassium hydroxide eluent generator cartridge
• Dionex CR‐ATC 500 continuously regenerated anion trap column
• Dionex AERS 500 anion electrolytically regenerated suppressor
• Chromeleon chromatography data system software, version 7.2

Methodology

Standards for target anions were prepared at 1000 mg/L and diluted to working levels (1–500 µg/L). Ethylenediamine (EDA) was added at 50 mg/L to preserve chlorite and bromate; sodium dichloroacetate (DCA) at 1 mg/L served as a surrogate. Samples were filtered through 0.45 µm filters. A hydroxide gradient (12–60 mM KOH over 30 min) was generated on‐line. Separation occurred on a guard and AS27 analytical column at 30 °C, 1.0 mL/min flow, and 250 µL injection, with suppressed conductivity detection.

Main Results and Discussion

The AS27 column achieved baseline resolution of chlorite, bromate, chlorate, bromide, and DCA in under 30 min, even in the presence of EDA artifacts. Calibration was linear over 1–500 µg/L (r2 > 0.999). Method detection limits (MDLs) were 0.10 µg/L for chlorite, 0.12 µg/L for bromate, 0.14 µg/L for chlorate, and 0.21 µg/L for bromide, representing a 60 % improvement over previous AS19‐based methods. Recoveries in three municipal waters and one high-ionic-strength sample ranged from 82.9 % to 108.2 %, meeting EPA Method 300.1 criteria. Precision was excellent (peak area RSD ≤ 3.2 %).

Benefits and Practical Applications

• Improved detection sensitivity and lower MDLs for trace oxyhalides and bromide
• Enhanced resolution of bromate from chloride and EDA‐induced artifacts
• Direct injection without postcolumn derivatization simplifies workflow
• On‐line hydroxide generation improves reproducibility across laboratories
• Applicable to regulatory compliance monitoring in drinking and high‐ionic‐strength waters

Future Trends and Potential Applications

Future developments may include coupling the AS27 column with mass spectrometric detection for even greater selectivity, further miniaturization of IC systems for field monitoring, and integration with automated sample preparation. Continued method refinement could extend applications to emerging disinfection byproducts and complex environmental matrices.

Conclusion

The Dionex IonPac AS27 column with RFIC eluent generation provides a robust, sensitive, and selective method for trace determination of oxyhalide disinfection byproducts and bromide in drinking water. It offers superior resolution, lower detection limits, and high accuracy in compliance with regulatory requirements.

Reference

1. U.S. EPA. Drinking Water Treatment; Document No. 810-F-99-013; Cincinnati, OH, 1999.
2. International Programme on Chemical Safety, WHO. Disinfectants and Disinfection By-Products; Environmental Health Criteria 216; Geneva, 2000.
3. Kemsley, J. Bromate in Los Angeles Water. Chem. Eng. News 2008, 85(52), 9.
4. Wagner, H.P.; Pepich, B.V.; Hautman, D.P.; Munch, D.J. J. Chromatogr. A 1999, 850, 119–129.
5. WHO. Bromate in Drinking Water–Background Document for WHO Guidelines; 2005.
6. U.S. Environmental Protection Agency. National Primary Drinking Water Regulations; Fed. Regist. 1998, 63(241), 69389–69476.
7. European Parliament and Council Directive 98/83/EC; Brussels, 1998.
8. Japanese Ministry Directive No. 101; Tokyo, 2002.
9. European Parliament and Council Directive 2003/40/EC; Brussels, 2003.
10. U.S. EPA Method 300.1: Determination of Inorganic Anions; 1997.
11. U.S. EPA Method 317.0: Oxyhalide DBPs in Drinking Water; 2001.
12. U.S. EPA Method 326.0: Oxyhalide DBPs with Acidified Postcolumn Reagent; 2002.
13. Thermo Scientific Application Note 167; 2004, revised 2014.
14. Thermo Scientific Application Note 168; 2005, revised 2013.
15. Thermo Scientific Application Note 171; 2006, revised 2013.
16. Thermo Scientific Application Note 187; 2007, revised 2013.