EPA Method 557 Quantitation of Haloacetic Acids, Bromate, and Dalapon in Drinking Water Using Ion Chromatography and Tandem Mass Spectrometry

Significance of the Topic

Haloacetic acids (HAAs), bromate and dalapon are common disinfection byproducts and pesticides found in drinking water that pose potential health risks at trace levels. Accurate and efficient quantitation of these analytes is critical for regulatory compliance and public health protection.

Objectives and Study Overview

This work describes the development and validation of EPA Method 557, an ion chromatography–tandem mass spectrometry (IC-MS/MS) technique for simultaneous analysis of nine HAAs, bromate, and dalapon in drinking water. The method aims to eliminate derivatization steps and extensive sample preparation, providing direct injection of water samples with high sensitivity and selectivity.

Methodology and Instrumentation

• Direct injection of preserved drinking water samples (100 mg/L NH4Cl) without pre-treatment.
• Reagent-free IC with electrolytically generated hydroxide eluent, using Dionex ICS-5000 system.
• Separation on Thermo Scientific Dionex IonPac AG24/AS24 columns and ASRS 300 suppressor.
• Timed diversion valves to remove high-matrix anions (chloride, sulfate, nitrate, bicarbonate) to waste.
• Detection by Thermo Scientific TSQ Endura triple quadrupole mass spectrometer with heated electrospray ionization (H-ESI-II) in negative mode.
• Use of 13C-labeled internal standards for quantitation and determination of method detection limits (MDLs).

Main Results and Discussion

• Excellent linearity (seven-point calibration) was achieved for all analytes from 0.25 µg/L to 20 µg/L in a simulated matrix of common drinking water ions.
• MDLs ranged from 0.021 ppb (DBAA) to 0.214 ppb (DBCAA), demonstrating sub-ppb sensitivity.
• Application to a San Jose tap water sample yielded a total of 35.62 ppb for all nine HAAs and 30.21 ppb for the regulated HAA5 group, below the EPA MCL of 60 ppb.
• The method effectively diverted matrix ions, protecting the MS source and ensuring clean ionization.

Benefits and Practical Applications

• Eliminates derivatization and extraction steps required in conventional EPA GC-ECD methods, reducing sample preparation time by several hours.
• Reagent-free eluent generation simplifies consumables management and improves gradient control.
• High selectivity and minimal interferences enable reliable quantitation in complex matrices.
• Direct injection workflow enhances laboratory throughput and reduces potential sample loss.

Future Trends and Opportunities

• Extension of IC-MS/MS methods to additional disinfection byproducts and emerging contaminants.
• Further improvements in sensitivity through alternative MS configurations or ionization techniques.
• Integration with automated on-line sample preparation and data processing for high-throughput monitoring.
• Application of this platform for routine compliance testing and real-time water quality assessment.

Conclusion

EPA Method 557 illustrates a powerful, streamlined IC-MS/MS approach for the quantitation of haloacetic acids, bromate, and dalapon in drinking water. The reagent-free system and direct injection protocol deliver high sensitivity, robust performance, and substantial time savings compared to traditional methods.

Reference

• U.S. Environmental Protection Agency. Microbial Health Effects Tables: Potential Adverse Health Effects from High/Long-term Exposure to Hazardous Chemicals in Drinking Water; 2002.
• U.S. Environmental Protection Agency. Method 552.1, Determination of Haloacetic Acids and Dalapon in Drinking Water by Ion Exchange Liquid-Solid Extraction and GC-ECD; Rev. 1.0; 1992.
• U.S. Environmental Protection Agency. Method 552.2, Determination of Haloacetic Acids and Dalapon in Drinking Water by Liquid-Liquid Extraction, Derivatization, and GC-ECD; Rev. 1.0; 1995.
• U.S. Environmental Protection Agency. Method 552.3, Determination of Haloacetic Acids and Dalapon in Drinking Water by Liquid-Liquid Microextraction, Derivatization, and GC-ECD; Rev. 1.0; 2003.
• U.S. Environmental Protection Agency. Method 557, Determination of Haloacetic Acids, Bromate, and Dalapon in Drinking Water by IC-ESI-MS/MS; Rev. 1.0; 2009.
• Slingsby R.; Saini C.; Pohl C.; Jack R. The Measurement of Haloacetic Acids in Drinking Water Using IC-MS/MS – Method Performance. Presented at Pittcon 2008.