Fast determination of nine haloacetic acids, bromate, and dalapon at trace levels in drinking water samples by tandem IC-MS/MS

Importance of the topic

The formation of haloacetic acids (HAAs), bromate, and dalapon as drinking water disinfection by-products (DBPs) poses potential health risks, including carcinogenicity and mutagenicity. Regulatory agencies such as the U.S. EPA and WHO have set stringent maximum contaminant levels for these compounds, driving the need for rapid, sensitive, and robust analytical methods to monitor trace concentrations in water supplies.

Objectives and overview of the study

This study aimed to develop and validate a fast ion chromatography–tandem mass spectrometry (IC-MS/MS) method for simultaneous determination of nine HAAs, bromate, and dalapon in drinking water. Using U.S. EPA Method 557 guidelines, the new approach leverages a Thermo Scientific Dionex™ IonPac™ AS31 column and a Thermo Scientific™ TSQ Fortis™ triple quadrupole mass spectrometer to reduce analysis time by 39% compared to the standard AS24 column method.

Methodology and Instrumentation

Water samples were preserved with ammonium chloride and injected directly (100 µL) without acidification or derivatization into a Dionex ICS-6000 system equipped with an eluent generator, dynamically regenerated suppressor, and conductivity detector. Separation was achieved on an AS31 guard/analytical column set, using a KOH gradient (17–85 mM) at 0.3 mL/min. A divert-valve scheme removed high-concentration common anions from the MS source, while 0.1 mL/min isopropanol enhanced ESI efficiency. Quantification employed isotope-labeled internal standards in SRM mode; linear ranges were 0.1–20 µg/L, with r2 ≥ 0.999. Method detection limits (MDLs) were 0.009–0.099 µg/L, and lowest concentration minimum reporting levels (LCMRLs) were 0.035–0.25 µg/L.

Instrumentation Used

• Dionex ICS-6000 IC system with dual analytical pump and eluent generator
• Dionex IonPac AS31 analytical and AG31 guard columns
• Dionex ADRS 600 dynamically regenerated suppressor
• Dionex AS-AP autosampler and low-temperature column compartment
• TSQ Fortis triple quadrupole mass spectrometer with ESI negative mode

Main Results and Discussion

The AS31 column achieved baseline separation of nine HAAs, bromate, and dalapon in 35 min, 39% faster than the AS24-based EPA 557 method, without compromising resolution. Matrix diversion improved MS signal intensities by up to 120% for early-eluting analytes. Precision studies (n=7) showed RSDs below 8%, and recoveries ranged from 90% to 110% at 2 µg/L spike levels. The method was successfully applied to groundwater, municipal, and bottled water samples; all analyte concentrations were below regulatory limits.

Benefits and Practical Applications of the Method

This direct IC-MS/MS approach eliminates time-consuming sample preparation steps such as derivatization and extraction, reducing potential losses and variability. The use of an eluent generator and suppression ensures a stable, reproducible baseline with minimal reagent handling. High sensitivity, robust suppression of interferences, and fast throughput make the method well suited for routine drinking water quality monitoring and regulatory compliance testing.

Future Trends and Potential Applications

Further developments may include two-dimensional IC to extend the range of detectable DBPs, integration with high-resolution mass spectrometry for non-target screening, and miniaturized field-deployable IC-MS/MS platforms. Advances in automation and software could streamline data processing and real-time decision support.

Conclusion

The validated IC-MS/MS method employing the Dionex IonPac AS31 column provides a rapid, sensitive, and robust solution for trace determination of nine HAAs, bromate, and dalapon in drinking water. It meets U.S. EPA performance requirements while cutting analysis time by nearly 40% and simplifying sample handling.

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