Determination of low-level haloacetic acids, bromate, and dalapon in drinking water using IC-MS

Importance of the topic

Disinfection byproducts such as haloacetic acids, bromate and dalapon pose health risks when present in drinking water. Rapid and sensitive monitoring methods are essential to ensure compliance with regulatory limits and protect public health.

Study objectives and overview

This study aimed to develop and validate a fast ion chromatography single quadrupole mass spectrometry (IC-MS) method to quantify nine haloacetic acids, bromate and dalapon in drinking water. The method builds on U.S. EPA Method 557 by replacing a longer IC gradient and tandem MS detection with a 40 min run using the Thermo Fisher Dionex ICS-6000 system, IonPac AS31 column, suppressed conductivity detector and ISQ EC single quadrupole MS.

Methodology and instrumentation

Standard and sample preparation included internal standards and synthetic matrix spiking. Separation was achieved on a 2 × 250 mm IonPac AS31 column with a hydroxide gradient and PEEK Viper tubing. The suppressed conductivity detector operated at 75 mA with the Dionex ADRS 600 suppressor. The ISQ EC single quad MS used negative electrospray ionization in selected ion monitoring mode with a diverter valve to protect the source from high salt. Temperature control at 15 °C in the autosampler and column compartment minimized analyte degradation.

Main results and discussion

Calibration over 0.01–100 µg L⁻¹ showed linearity (r² ≥ 0.998). Method detection limits for regulated HAA5 ranged from 0.03 to 0.67 µg L⁻¹ and 0.12 µg L⁻¹ for bromate and dalapon. Spike recoveries at 10 µg L⁻¹ in a synthetic matrix were 92–119 % for ten analytes. Real tap water samples showed concentrations below EPA limits with consistent precision (RSD < 13 %). Instrument maintenance of the regenerant trap and low background conductivity were critical for sensitivity.

Benefits and practical applications

The proposed IC-MS workflow reduces analysis time by one third compared to existing methods, lowers operating cost by using a single quadrupole MS, and achieves regulatory detection requirements. The method offers a streamlined approach for routine monitoring of disinfection byproducts in water utilities and laboratories.

Future trends and opportunities

Further improvements may include coupling IC to triple quadrupole or high-resolution MS for lower detection limits and enhanced selectivity in complex matrices. Miniaturization of suppressors and more robust diverter valve designs will increase instrument uptime and reduce maintenance.

Conclusion

A rapid 40 min IC-MS method using a single quadrupole MS meets EPA Method 557 guidelines for HAA5, bromate and dalapon determination in drinking water. The approach offers adequate sensitivity, linearity and recovery while improving throughput and reducing hardware complexity.

Reference

• U.S. EPA Method 557 Determination of Haloacetic Acids, Bromate, and Dalapon in Drinking Water by IC-ESI-MS/MS.
• Thermo Scientific Dionex ICS-6000 and ISQ EC Instrumentation Manuals.