Haloacetic Acid Analysis Using Ion Chromatography (IC) Followed by Triple Quadrupole Mass Spectrometry (MS) Detection

Importance of the Topic

Haloacetic acids (HAAs) are common disinfection by-products formed when chlorine reacts with natural organic matter in water. Several HAAs are regulated due to their potential health impacts, including risks of cancer and reproductive issues. Ensuring accurate, reliable, and efficient analysis of HAAs at low concentration levels is critical for drinking water safety and regulatory compliance.

Objectives and Study Overview

This application note evaluates a direct injection ion chromatography (IC) method coupled with triple quadrupole mass spectrometry (TQ MS) for quantifying nine haloacetic acids (HAA9) in water following US EPA Method 557. The goals include demonstrating method performance criteria, achieving low reporting levels, and validating spike recoveries in synthetic and real water matrices.

Methodology and Instrumentation

Water samples (10 mL) were preserved with ammonium chloride, spiked with 10 ng/mL of uniformly labeled internal standards, and directly injected into the IC system. A Metrosep A SUPP 7 (250 mm × 4 mm) column was used with a potassium hydroxide/methanol gradient and chemical suppressor regenerated by 1 M nitric acid with 5% methanol. The Metrohm 940 Professional IC Vario was coupled to an Agilent 6470B TQ LC/MS operated in dynamic multiple reaction monitoring (MRM) mode. Calibration covered 0.5–40 ng/mL (2 ng/mL for TBAA) with a seven-point curve, and data acquisition was managed via MagicNet and MassHunter software.

Main Results and Discussion

• Chromatographic separation achieved baseline resolution of all nine HAAs in a 40 min run.
• Reporting limits were 0.5 µg/L for most HAAs and 2 µg/L for tribromoacetic acid (TBAA).
• Calibration curves were linear (R² > 0.99) with acceptable accuracy (±20%).
• Spike recoveries in synthetic matrix ranged from 86% to 104%; in tap water from 72% to 121%.
• Precision (RSD) was 10–12% for most analytes; TBAA showed 20% RSD.
• No significant background or carry-over was observed; reagent blanks remained below one-third of the method reporting limit.
• Native drinking water samples contained total HAA9 levels < 19 µg/L, well under the 60 µg/L regulatory limit; in-home filtration reduced HAA9 from 19 µg/L to 2.6 µg/L.

Benefits and Practical Applications of the Method

• Direct injection reduces sample preparation time and operator workload compared to derivatization GC-ECD methods.
• MRM with isotope-labeled internal standards corrects for variability and matrix effects, enhancing accuracy.
• High selectivity and sensitivity allow compliance with EPA performance criteria and detection at sub-µg/L levels.
• Robustness and automation support routine monitoring in environmental and drinking water laboratories.

Future Trends and Potential Applications

Emerging directions include integration with high-resolution mass spectrometry for comprehensive disinfection by-product screening, miniaturized and portable IC-MS devices for field analysis, and automated online sampling for near real-time monitoring. Application of this approach to additional regulated and unregulated by-products can expand water quality surveillance capabilities.

Conclusion

The direct IC–TQ MS method following EPA 557 provides a streamlined, sensitive, and accurate workflow for quantifying nine HAAs in drinking water. It meets regulatory requirements, delivers reliable performance in diverse matrices, and offers significant advantages over traditional techniques in terms of speed and robustness.

References

• US EPA Method 557: Determination of Haloacetic Acids, Bromate, and Dalapon in Drinking Water by IC-ESI-MS/MS.
• US EPA Method 552.2: Determination of Haloacetic Acids and Dalapon by GC-ECD.
• Metrohm Application Note M-15: Trace Haloacetic Acids, Dalapon, and Bromate in Water (IC-MS/MS).
• Agilent Technologies Application Note 5991-6417EN: Analysis of Haloacetic Acids by IC-TQ LC/MS.