Determination of trace concentrations of oxyhalides and bromide in municipal and bottled waters by IC

Importance of the Topic

Monitoring inorganic oxyhalides and bromide at trace levels is critical for ensuring drinking water safety and complying with regulatory standards such as the U.S. EPA’s SDWA and CWA. Oxyhalides like chlorite, chlorate, and bromate can form disinfection by-products during water treatment, posing health risks. Sensitive, reliable, and rapid analytical methods are essential for quality control in municipal and bottled water.

Objectives and Study Overview

The study aimed to develop and validate a sensitive ion chromatography (IC) method for simultaneous determination of trace oxyhalides and bromide in drinking water. Utilizing the compact Dionex Inuvion RFIC system, the method seeks rapid separation, low detection limits, and operational simplicity for regulatory compliance monitoring.

Instrumentation

• Dionex Inuvion single-channel IC system with peristaltic pump
• Dionex AS-DV autosampler with 5 mL vials and filter caps
• Dionex IonPac AG23-4µm (4 × 50 mm) and AS23-4µm (4 × 250 mm) column set
• RFIC eluent generator cartridge (EGC K2CO3) and EPM 500 pH modifier
• Dionex AERS 500 suppressor (electrolytic) and CRD 300 carbonate removal device
• Chromeleon CDS software version 7.3.3

Methodology and Sample Preparation

The eluent comprised 4.5 mM Na2CO3/0.8 mM NaHCO3 generated in-line. Suppressed conductivity detection used carbonate suppression followed by chemical regeneration with 200 mM NaOH delivered via peristaltic pump. Water samples, including municipal and bottled sources, were analyzed directly and spiked at 10 µg/L and 50 µg/L levels. Full loop injections (250 µL) were performed at a 1.0 mL/min flow rate and 30 °C column temperature.

Main Results and Discussion

The method achieved baseline separation of ten inorganic anions within 30 minutes. Trace levels of chlorite (5.4 µg/L), chlorate (77.1 µg/L), and bromide (13.3 µg/L) were quantified in tap water, with no detectable bromate, meeting U.S. EPA limits (chlorite 1000 µg/L, bromate 10 µg/L) and EU chlorate MRL of 0.01 ppm. Spike recoveries demonstrated linearity and sensitivity for regulatory compliance.

Benefits and Practical Applications

• Rapid, robust separation suitable for high-throughput routine monitoring
• Low detection limits for regulatory analytes in complex matrices
• Compact, integrated system reduces instrument footprint and maintenance
• Reagent-free eluent generation enhances reproducibility and lowers operating costs

Future Trends and Potential Applications

Advancements in RFIC technology may further lower detection limits for emerging contaminants. Integration with mass spectrometry could expand multi-class analyte screening. Automated sampling and data processing will streamline compliance workflows in drinking water and environmental monitoring.

Conclusion

The Dionex Inuvion RFIC method offers a sensitive, efficient, and compact solution for the determination of oxyhalides and bromide in drinking water, supporting regulatory compliance and ensuring public health protection.

Reference

1. U.S. EPA Method 300.1, The Determination of Inorganic Anions in Water by Ion Chromatography; 1997.
2. Thermo Scientific Application Note 72209, Determination of Trace Concentrations of Oxyhalides and Bromide in Municipal and Bottled Waters; 2011.
3. The Third Unregulated Contaminant Monitoring Rule (UCMR 3).
4. EU Maximum Residue Level for Chlorate in Food Products.