Analysis of Bromate in Tap Water Using a Triple Quadrupole LC/MS/MS (2)

Significance of the Topic

Bromate is a potential carcinogenic by-product formed during ozone-based water treatment. Regulatory bodies such as IARC classify it as possibly carcinogenic, and many countries, including Japan, enforce strict limits on its concentration in drinking water. Reliable, sensitive, and efficient analytical methods are essential to ensure compliance with water quality standards and protect public health.

Objectives and Study Overview

This study evaluates a novel LC/MS/MS method for quantifying bromate in tap water using a mixed-mode chromatography column. The goal was to establish robust separation conditions, assess calibration performance at regulatory threshold levels (0.01 mg/L) and below (0.001 mg/L), and validate the approach via spike-and-recovery experiments in real tap water samples.

Methodology and Instrumentation

Chromatographic separation was achieved on an Imtakt Scherzo SS-C18 mixed-mode column (150 mm × 2.0 mm I.D., 3 μm) combining reversed-phase and anion-exchange interactions.

• Mobile phase A: 200 mmol/L ammonium acetate in water with 0.5 % acetic acid
• Mobile phase B: Acetonitrile
• Gradient: 90 % B (0–7 min) → 5 % B (7.01–12 min) → 90 % B (12.01–17 min)
• Flow rate: 0.3 mL/min; Column temperature: 40 °C; Injection volume: 10 µL

Mass spectrometric detection used a triple-quadrupole LC/MS/MS system in negative ESI mode with MRM transition m/z 129.00 → 112.95. Source conditions included probe voltage –1 kV, DL 100 °C, block heater 300 °C, interface 300 °C, nebulizing gas 2 L/min, drying and heating gas 10 L/min.

Main Results and Discussion

The mixed-mode column provided strong retention of highly polar bromate, eluting at 2.7 min with excellent peak shape. Calibration from 0.0005 to 0.01 mg/L yielded outstanding linearity (R = 0.9995, R2 = 0.9990). Separation of bromate from common anions in tap water (sulfate, chloride, nitrate, chlorate) was confirmed, enhancing selectivity. A switching valve diverted high-salt fractions away from the MS detector between 7 and 15 min to maintain instrument robustness.

Benefits and Practical Applications

This LC/MS/MS approach eliminates the need for post-column derivatization or reagent preparation, reducing analysis time and operational complexity. It reliably quantifies bromate at one-tenth of the regulatory limit without extensive sample preparation, making it suitable for routine water quality monitoring in environmental and municipal laboratories.

Future Trends and Potential Applications

Emerging directions include automated online monitoring platforms integrating mixed-mode LC/MS/MS for real-time water analysis, miniaturized flow-through devices for field deployment, and coupling with high-resolution mass spectrometry to extend applications to other polar contaminants. Advances in column chemistry and instrument sensitivity will further lower detection limits and increase throughput, supporting comprehensive water safety programs.

Conclusion

The mixed-mode LC/MS/MS method demonstrates high sensitivity, selectivity, and reliability for bromate determination in tap water at regulatory levels and below. Its streamlined workflow and robust performance offer significant advantages over traditional approaches, positioning it as a valuable tool for ensuring drinking water safety.

Reference

Tanaka M., Horiike H. Analysis of Bromate in Tap Water Using a Triple Quadrupole LC/MS/MS. Application News No. C152. Shimadzu Corporation; May 2017.