Speciation of Bromine Compounds in Ozonated Drinking Water using Ion Chromatography and Inductively Coupled Plasma Mass Spectrometry

Significance of the topic

Monitoring bromine species in drinking water is critical due to the carcinogenic nature of bromate, a by-product of ozonation used for disinfection. Regulatory bodies in the United States and Europe limit bromate levels to protect public health. Accurate speciation between non-toxic bromide and toxic bromate is essential for compliance and risk assessment.

Objectives and study overview

This study applied the EPA Method 321.8 protocol to separate, detect and quantify bromide and bromate in bottled and tap water samples. The goal was to demonstrate a direct, interference-free analytical workflow that meets regulatory detection limits without extensive sample pretreatment.

Methodology

Water samples and calibration standards were adjusted to pH 10 and introduced directly for analysis. A KOH gradient eluent provided baseline resolution of bromine species on an anion exchange column. The ICP-MS was operated in kinetic energy discrimination mode (He-KED) to remove polyatomic interferences on mass 79 and 81. External calibration curves covered 1 to 25 micrograms per liter with correlation coefficients exceeding 0.999. Method detection limits were determined from replicate analyses according to EPA guidelines.

Used Instrumentation

• Thermo Scientific Dionex ICS-5000 ion chromatography system with eluent generator
• Thermo Scientific iCAP Q ICP-MS equipped with QCell collision cell operated in He-KED mode
• Thermo Scientific Dionex AS-AP autosampler
• Thermo Scientific Chromeleon and Qtegra chromatography data systems

Main results and discussion

Calibration linearity was consistently better than 0.999 over three days. Spike recoveries for bromate were quantitative (average 99.8% ± 0.4%). A method detection limit of 0.014 micrograms per liter for bromate was achieved, far below the US EPA requirement of 0.3 micrograms per liter and well under the maximum contaminant levels. Chloride, sulfate and phosphate interferences were effectively eliminated by He-KED, as demonstrated by comparison with standard mode. Chromatograms showed baseline separation of bromide, bromate and minor brominated by-products.

Benefits and practical applications

• Direct analysis without chloride removal or derivatization
• Tolerance of high salt matrices and minimal sample preparation
• High sensitivity and reproducibility for regulatory compliance
• Rapid turnaround suitable for routine QA/QC in water treatment facilities

Future trends and potential applications

Advances may include automated online sampling, expansion of the method to other halogenated disinfection by-products, coupling with high-resolution mass spectrometry for structural identification, and integration into real-time water monitoring networks. Data analytics and machine learning could further improve detection of emerging contaminants.

Conclusion

The combined use of ion chromatography and ICP-MS with He-KED interference removal provides a robust, sensitive and regulatory-compliant approach for bromine speciation in drinking water. Method 321.8 enables accurate quantification of bromide and bromate with minimal sample handling and detection limits well below required standards.

References

1. ISO 11206 Water quality – Determination of polyhalogenated acetic acids by ion chromatography
2. EPA Method 326.0 and 317.0 Determination of inorganic oxhalide disinfectant by-products in drinking water using ion chromatography
3. EPA Method 300.0 and 300.1 Determination of inorganic anions by ion chromatography
4. EPA Method 321.8 Determination of bromate in drinking waters by ion chromatography coupled with inductively coupled plasma mass spectrometry