Analysis of Bromate in Tap Water Using a Triple Quadrupole LC/MS/MS (1)

Significance of the Topic

Bromate is a regulated disinfection byproduct formed during ozonation of drinking water. Classified as a possible human carcinogen by IARC, it is subject to strict quality standards. Rapid and sensitive detection of trace bromate in tap water is therefore essential for public health monitoring and regulatory compliance.

Objectives and Study Overview

This study evaluates a proposed LC MS/MS method for bromate analysis in tap water using an anion exchange column under conditions compatible with routine reversed phase LC MS workflows. Key goals include establishing retention and separation of bromate, assessing calibration linearity, verifying selectivity against common anions, and determining accuracy and precision in real tap water samples.

Methodology and Instrumentation

An anion exchange column was paired with mobile phases and mass spectrometry settings to achieve reliable bromate detection:

• Column: GL Sciences SYPRON AX-1 100 mm × 2.1 mm I D 5 μm
• Mobile phases: 25 mmol/L ammonium acetate in water (A) and acetonitrile (B) at 70/30 vol/vol
• Flow rate 0.2 mL/min, column temperature 40 C, injection volume 10 μL
• ESI negative ion mode, probe voltage 1 kV, interface and heater 300 C, DL 100 C
• MRM transition m/z 129.00 > 112.95 for bromate

Key Results and Discussion

Bromate eluted at 3.4 minutes with a sharp peak. A five-point calibration from 0.0005 to 0.01 mg/L yielded linearity with R = 0.999 and R2 = 0.998. Chromatograms confirmed clear separation from sulfate, chloride, nitrate and chlorate impurities, despite using a moderate 25 mmol/L buffer concentration, minimizing instrument maintenance. Spike-and-recovery tests in Kanagawa tap water at 0.01 mg/L and 0.001 mg/L bromate achieved recoveries of 96.7 with 2.2 RSD and 84.6 with 5.2 RSD respectively, meeting validation criteria without sample pretreatment.

Benefits and Practical Applications

This LC MS/MS approach eliminates reagent preparation required for post column detection, reduces analysis time and labor, and improves throughput for routine water quality testing. High sensitivity and selectivity support compliance with regulatory limits and enable reliable monitoring of bromate at one tenth of the standard criterion.

Future Trends and Applications

Building on this method, future work may explore:

• Extension to other anionic disinfection byproducts
• Integration with automated sample preparation and high-throughput platforms
• Adaptation to portable MS systems for on site water monitoring
• Use of alternative buffers or columns to further enhance selectivity

Conclusion

The proposed anion exchange LC MS/MS method delivers sensitive, accurate and efficient detection of bromate in tap water down to 0.001 mg/L. Its robust performance and minimal maintenance needs make it well suited for routine water quality laboratories and regulatory compliance testing.

References

• IARC Monographs on the Evaluation of Carcinogenic Risks to Humans 1999
• Ministry of Health Labour and Welfare Japan Notification No 261 2016
• Validation Guidelines MHLW September 2012
• Shimadzu Application Note LAAN A LM E115