Determination of Disinfection Byproduct Anions and Bromide in Drinking Water Using a Reagent-Free Ion Chromatography System Followed by Postcolumn Addition of an Acidified On-Line Generated Reagent for Trace Bromate Analysis

Significance of the Topic

Municipal water treatment often relies on disinfectants such as chlorine dioxide, chloramine, and ozone to control pathogens. These processes generate disinfection byproducts (DBPs) like chlorite, chlorate, and bromate, which pose potential health risks at trace levels. Regulatory agencies such as the U.S. EPA and WHO have established stringent limits (e.g., 10 µg/L for bromate) to protect consumers. Accurate, sensitive analysis of these oxyhalide DBPs and related anions is essential for compliance monitoring, risk assessment, and water quality management.

Objectives and Study Overview

This application note demonstrates a method for simultaneous determination of DBP anions (chlorite, chlorate, bromate) and bromide in drinking water using a reagent-free ion chromatography (RFIC) system with postcolumn acidified potassium iodide reagent and dual detection (suppressed conductivity and UV absorbance). The approach leverages a novel hydroxide-selective IonPac AS19 column to improve sensitivity and selectivity compared to traditional carbonate-based methods, targeting method detection limits compatible with current EPA regulations.

Methodology

An electrolytically generated potassium hydroxide gradient eluent (10–45 mM KOH) was delivered at 1.0 mL/min through a Dionex IonPac AG19 guard and AS19 analytical column (4 × 250 mm). Postcolumn, the effluent mixed with 0.26 M KI/43 µM ammonium molybdate reagent at 0.3 mL/min in an 80 °C knitted coil for in situ triiodide formation. Detection employed an ASRS 300 suppressor (external water mode) with suppressed conductivity and a UV detector set at 352 nm. Samples were preserved with ethylenediamine, filtered, and spiked with a malate surrogate to monitor recovery.

Used Instrumentation

• Thermo Scientific Dionex ICS-3000 RFIC with DP/SP pump, EG EluGen EGC II KOH cartridge, and CR-ATC trap column
• Dionex IonPac AG19 guard (4 × 50 mm) and AS19 analytical column (4 × 250 mm)
• ASRS 300 and AMMS 300 suppressors
• PC10 postcolumn pneumatic delivery module and RCH-1 reaction heater
• VWD UV/Vis absorbance detector (352 nm, PEEK flow cell)
• Chromeleon chromatography management software

Main Results and Discussion

The method achieved excellent linearity (r2 ≥ 0.999) over calibration ranges of 5–500 µg/L for chlorite, chlorate, and bromide, 1–50 µg/L for bromate by conductivity, and 0.5–15 µg/L by UV. Method detection limits were 0.6 µg/L (chlorite), 1.0 µg/L (chlorate), 1.9 µg/L (bromide), 0.12 µg/L (bromate conductivity), and 0.17 µg/L (bromate UV). Recoveries in fortified tap and bottled waters ranged from 90–112%, meeting EPA Method 326.0 criteria. Chromatograms demonstrated baseline separation of DBP anions and bromide, and enhanced bromate sensitivity with UV detection. A 21-day ruggedness study yielded ≤9.2% RSD in bromate area and ≤0.9% RSD in retention time. The malate surrogate was well-resolved from carbonate and analytes, providing reliable QA/QC monitoring.

Benefits and Practical Applications

• Reagent-free IC reduces chemical handling and baseline noise compared to carbonate eluents
• Hydroxide-selective AS19 column enhances separation and lowers MDLs for bromate and other DBPs
• Postcolumn KI reagent with UV detection achieves sub-µg/L bromate quantification without carcinogenic reagents
• Method conforms to EPA Method 326.0 for regulatory compliance and routine monitoring

Future Trends and Potential Applications

Advances in reagent-free IC and column selectivity are expected to lower detection limits further and streamline DBP analysis in complex matrices. Integration with automated sample preparation, broader DBP speciation (e.g., haloacetic acids), and coupling with mass spectrometric detection may expand applicability in environmental and industrial water quality studies.

Conclusion

The combination of an RFIC system with a hydroxide-selective AS19 column and postcolumn acidified KI reagent provides a robust, sensitive, and selective method for trace determination of oxyhalide DBPs and bromide in drinking water. It delivers low detection limits, high accuracy, and compliance with regulatory requirements while minimizing hazardous reagents.

Reference

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