Determination of Bromate by ISO Method 11206

Significance of the Topic

Ozonation of drinking and bottled waters is widely used due to its strong disinfection power and lack of residual taste. However, when bromide ions are present, ozonation converts them to bromate, a potential human carcinogen. Regulatory bodies such as the U.S. EPA and the European Commission limit bromate levels to 10 µg/L for drinking water and 3 µg/L for bottled natural mineral water. Thus, highly sensitive and robust analytical methods are essential for monitoring bromate to ensure water safety and regulatory compliance.

Objectives and Overview of the Study

The purpose of ISO Method 11206 is to provide an improved protocol for trace-level determination of bromate in ozonated waters using ion chromatography coupled with postcolumn derivatization. The study aims to enhance sensitivity over previous ISO and EPA methods and to simplify analysis by eliminating complex sample preparation. Key objectives include:

• Developing a postcolumn triiodide reaction to boost detection sensitivity by more than tenfold.
• Demonstrating compatibility with a range of anion-exchange columns using a methanesulfonic acid eluent.
• Achieving detection limits below 0.1 µg/L without heating the reaction coil.

Methodology and Instrumentation

The ISO 11206 protocol utilizes isocratic ion chromatography with a latex-based anion-exchange column (e.g., CarboPac PA1) and a 200 mM methanesulfonic acid eluent at 1.0 mL/min. A potassium iodide solution acidified to pH ≤1 is added postcolumn via a second pump. In the reaction coil, generated hydroiodic acid reacts with bromate to form triiodide, which is detected by UV absorbance at 352 nm. No additional sample preparation is required. Limits of detection (LOD) and quantification (LOQ) are determined at signal-to-noise ratios of 3 and 10, respectively.

Used Instrumentation

• Thermo Scientific Dionex ICS-5000 IC system with dual pump, conductivity detector, variable wavelength detector, and autosampler.
• Thermo Scientific Dionex CarboPac PA1 column, 4 × 250 mm.
• Reagent-Free™ IC system for on-demand eluent generation.
• Chromeleon 7.1 chromatography data system.

Main Results and Discussion

Under optimized conditions, bromate is baseline-separated in under 18 minutes with a 500 µL injection volume. The method achieves an LOD of 0.07 µg/L and an LOQ of 0.22 µg/L. Using methanesulfonic acid rather than sulfuric acid increases column compatibility and application flexibility. The low-pH derivatization prevents chlorite interference and eliminates the need for reaction coil heating, simplifying the setup.

Benefits and Practical Applications

The ISO 11206 method offers significant advantages for routine water quality monitoring:

• Enhanced sensitivity suitable for regulatory limits below 3 µg/L.
• Reagent-free eluent generation for improved reproducibility and reduced maintenance.
• Direct injection without sample pretreatment, increasing throughput.
• Compatibility with multiple anion-exchange columns, allowing tailored selectivity.

Future Trends and Opportunities

Advances in two-dimensional ion chromatography and on-line preconcentration techniques are likely to further lower detection limits and expand applicability to complex matrices. Integration with mass spectrometric detection may provide additional selectivity. Continued development of reagent-free systems and novel column materials will enhance robustness and simplify regulatory compliance in water analysis.

Conclusion

ISO Method 11206 presents an efficient, highly sensitive approach for bromate determination in ozonated waters. By leveraging postcolumn derivatization, reagent-free eluent generation, and a simplified workflow, the method meets stringent regulatory requirements and supports high-throughput monitoring.

Reference

1. U.S. EPA. National Primary Drinking Water Regulations: Disinfectants and Disinfection Byproducts. Federal Register 1998, 63(241), 69389–69476.
2. Commission Directive 2003/40/EC. Official Journal of the European Union, 2003.
3. Djoukeng J.; Jensen D. Ion chromatographic determination of oxyhalides and bromide in drinking water by direct injection. Thermo Fisher Application Note, 1997.
4. Djoukeng J.; Jensen D. Determination of inorganic oxyhalide anions and bromide using postcolumn reagent for trace bromate analysis. Thermo Fisher Application Note, 2004.
5. Djoukeng J.; Jensen D. Determination of chlorite, bromate, bromide and chlorate in drinking water using on-line-generated postcolumn reagent. Thermo Fisher Application Note, 2003.
6. Thermo Scientific. Ion chromatography with reagent-free eluent generation: Application Note 167, 2004.
7. ISO 11206:2011. Water Quality — Determination of Dissolved Bromate by IC and Postcolumn Reaction. Beuth Verlag, Berlin, 2011.