Determination of Disinfection By-Products in Drinking Water According to EPA Method 326.0

Importance of the Topic

Disinfection by-products (DBPs) such as chlorite, chlorate, bromate and bromide are generated during chemical treatment of drinking water and can pose significant health risks. Regulatory agencies, including the U.S. EPA, set strict limits for these inorganic oxyhalide by-products to protect public health. Reliable, sensitive and rapid analytical methods are essential for routine monitoring and compliance.

Aims and Study Overview

This work demonstrates the application of EPA Method 326.0 for quantifying key DBPs in drinking water using the Shimadzu Nexera lite inert ion chromatography system. The study aims to optimize separation, detection and quantification of chlorite, bromate, bromide and chlorate with minimal analysis time and high reproducibility across diverse water matrices.

Instrumentation

• High-performance liquid chromatograph: Shimadzu Nexera lite inert
• Analytical column: Shim-pack IC-SA3 (4.0 mm × 250 mm, 5 µm) with Shim-pack IC-SA3 guard column
• Eluent: 3.6 mmol/L Na₂CO₃, flow rate 0.8 mL/min
• Suppressor: electrically regenerable, flow rate 0.8 mL/min
• Post-column reagent: 0.16 mol/L KI and 0.035 mmol/L (NH₄)₆Mo₇O₂₄•4H₂O mixed 50:50 with 0.5 mol/L H₂SO₄, flow rate 0.4 mL/min
• Reaction coil: 0.5 mm × 1 m; post-column degassing: DGU-10B with N₂
• Injection volume: 300 µL; column temperature: 40 °C
• Detectors: conductivity detector for general DBPs; UV detector at 352 nm for bromate

Methodology

EPA Method 326.0 procedures were followed, including addition of dichloroacetic acid (DCA, 1 mg/L) as a surrogate and ethylenediamine to stabilize analytes. Standard calibration employed six-point curves for conductivity detection (5–200 µg/L, r² > 0.999) and five-point curves for UV detection of bromate (0.5–10 µg/L, r² > 0.9999). Detection limits were determined by replicate analysis: conductivity DLs ranged from 0.4 to 1.0 µg/L; UV DL for bromate was 0.08 µg/L, with LOQ at 0.3 µg/L. Sample pretreatment for high-matrix waters utilized a 0.5 mL Maxi-Clean IC-H cartridge to remove interfering cations.

Main Results and Discussion

Reproducibility and accuracy met EPA QC criteria, with conductivity detector recoveries between 95 and 113 % (RSD ≤ 4.1 %) and UV detector recoveries between 99 and 101 % (RSD ≤ 1.2 %). Bromate LOQ satisfied the European limit of 3 µg/L for ozonated bottled waters. Spike recoveries (84–106 %) and relative percent differences (< 10 %) across six drinking water types confirmed method robustness. Cartridge pretreatment improved peak shapes in high ionic strength samples.

Benefits and Practical Applications

The described method enables complete DBP profiling in approximately 15 minutes, offering high sensitivity, reproducibility and selectivity, particularly for trace bromate. It is well suited for routine QA/QC, regulatory compliance and environmental monitoring laboratories.

Future Trends and Potential Applications

Advances may include inline coupling with mass spectrometry for broader DBP characterization, miniaturized portable IC systems for on-site monitoring, integration with automated sample preparation, and application of chemometric and AI-based data analysis to improve throughput and interpret complex datasets.

Conclusion

The application of EPA Method 326.0 on the Nexera lite inert platform provides a rapid, reliable and sensitive approach for quantifying inorganic oxyhalide disinfection by-products, ensuring compliance with regulatory limits and supporting public health protection.

References

• U.S. Environmental Protection Agency. Method 326.0: Determination of Inorganic Oxyhalide Disinfection By-Products in Drinking Water Using Ion Chromatography Incorporating the Addition of a Suppressor Acidified Postcolumn Reagent for Trace Bromate Analysis, Version 1.0.
• European Commission. Commission Directive 2003/40/EC of 16 May 2003 amending Council Directive 98/83/EC on the quality of water intended for human consumption.