EPA Method 557 – Analysis of Haloacetic Acids, Dalapon, and Bromate in Drinking Water by IC-MS/MS

Importance of Topic

Water disinfection produces haloacetic acids (HAAs) and bromate, which pose long-term health risks such as cancer. Monitoring these contaminants at low concentrations in drinking water is critical for regulatory compliance and public health protection. A streamlined, sensitive analysis method reduces lab workload and enhances data reliability.

Study Objectives and Overview

This work demonstrates EPA Method 557, which combines ion chromatography with tandem mass spectrometry (IC-MS/MS) to directly quantify five regulated HAAs, four unregulated HAAs, dalapon, and bromate in drinking water, without derivatization or extensive sample preparation. The goal was to achieve rapid, robust analysis while meeting or exceeding detection limits of established GC-ECD methods.

Methodology and Instrumentation

• Ion Chromatography: Thermo Scientific Dionex ICS-5000+ RFIC system with an AS24 analytical column and AERS 500 suppressor; electrolytic KOH gradient eluent; isopropyl alcohol makeup flow; six-port diversion valve to remove inorganic matrix.
• Mass Spectrometry: Thermo Scientific TSQ Endura triple quadrupole MS with HESI-II source in negative mode; optimized RF lens voltages and collision energies for each analyte; source temperatures adjusted to 200 °C for optimal trichloroacetic acid response.
• Data Analysis: Thermo Scientific TraceFinder software v3.2 for quantitation using 13C-labeled internal standards.

Main Results and Discussion

Calibration curves (0.25–20 µg/L) exhibited excellent linearity for all analytes. Method detection limits ranged from 0.021–0.214 µg/L, surpassing EPA Method 552.2 for most compounds. Analysis of synthetic matrix and municipal San Jose water (total HAA5 = 30.21 µg/L; total HAA9 = 35.62 µg/L; bromate = 0.44 µg/L) confirmed method accuracy, precision (%RSD < 11%), and compliance below the 60 µg/L maximum contaminant level.

Practical Benefits and Applications

• Eliminates derivatization and multi-step extraction, reducing analysis time by several hours.
• Minimizes use of toxic reagents and solvent consumption.
• Provides high selectivity via matrix diversion and IC-MS/MS, resulting in cleaner MS source and consistent performance.
• Enables flexible runtime: full panel in 58 min or five regulated HAAs in 45 min with minimal method adjustments.

Future Trends and Applications

Advancements may include higher-throughput IC-MS/MS platforms, alternative eluent strategies for faster separations, and expanded target lists covering emerging disinfection by-products. Integration with automated sample preparation and real-time data reporting will further support regulatory monitoring and water quality management.

Conclusion

EPA Method 557 using RFIC-MS/MS delivers a simplified, sensitive, and robust solution for simultaneous quantitation of nine HAAs, dalapon, and bromate in drinking water. The approach outperforms traditional GC-ECD methods in speed, safety, and detection limits, ensuring reliable compliance monitoring and protecting public health.

Reference

1. U.S. EPA, Microbial Health Effects Tables, 2002.
2. U.S. EPA Method 552.1, Rev. 1.0, 1992.
3. U.S. EPA Method 552.2, Rev. 1.0, 1995.
4. U.S. EPA Method 552.3, Rev. 1.0, 2003.
5. U.S. EPA Method 557, Rev. 1.0, 2009.
6. Slingsby R., Saini C., Pohl C., Jack R., IC-MS/MS Haloacetic Acid Measurement, Pittcon 2008.
7. U.S. EPA, Basic Information on Disinfection Byproducts, online.