Determination of Chlorite, Chlorate and Bromate in Water by Suppressed Anion Chromatography Coupled with Mass Spectrometry

Significance of the Topic

Effective monitoring of disinfection byproducts (DBPs) such as chlorite, chlorate and bromate in drinking water is crucial for public health protection. These oxyhalides can form during water treatment processes using chlorine, chlorine dioxide or ozone, and bromate is classified as a potential human carcinogen with strict regulatory limits (e.g., 10 ppb by the US EPA). Reliable, sensitive analytical methods are needed to ensure compliance and assess treatment efficacy.

Objectives and Study Overview

The study presents the development and validation of an ion chromatography–mass spectrometry (IC-MS) method for simultaneous determination of chlorite, chlorate and bromate in water. The goals included achieving low detection limits (<0.5 ppb), high precision and accuracy without extensive sample preparation, and demonstration of robustness in diverse water matrices.

Methodology and Instrumentation

The analytical system comprises a Shimadzu Prominence modular IC with an electrolytically regenerated suppressor and an LCMS-2020 single quadrupole mass spectrometer equipped with negative-mode electrospray ionization. Key features:

• Anion separation by suppressed IC.
• Post-column divert valve directing only target oxyhalides to MS.
• Conductivity detection for effluent monitoring and method control.
• Selected ion monitoring (SIM) on two isotopic masses per compound for quantitation.

Main Results and Discussion

Calibration was linear over 0.5–100 ppb for chlorite/chlorate and 0.5–25 ppb for bromate, with correlation coefficients (r2) above 0.999. Precision tests at three concentration levels (0.5, 1, 10 ppb) yielded relative standard deviations below 6.5%, and recoveries from spiked real water samples ranged from 84.1% to 113.6%. Typical retention times were 10.5 min for chlorite, 10.9 min for bromate and 18.8 min for chlorate, with clear isotopic peak ratios confirming identity.

Benefits and Practical Applications

The method combines high sensitivity, minimal sample handling, and unambiguous mass confirmation. It is suitable for regulatory compliance monitoring in drinking water utilities, quality control in treatment plants, and research on DBP formation mechanisms.

Future Trends and Potential Applications

Advances may include integration with high-resolution MS for enhanced specificity, miniaturized IC systems for on-site monitoring, and automated data processing for real-time water quality assessment. Expansion to additional inorganic ions and emerging contaminants is also anticipated.

Conclusion

The developed IC-MS protocol offers a robust, reproducible and sensitive approach for simultaneous determination of chlorite, chlorate and bromate in drinking water. Its low detection limits, excellent precision and straightforward workflow make it a valuable tool for environmental monitoring and water safety assurance.