Determination of Trace Concentrations of Oxyhalides and Bromide in Municipal and Bottled Waters Using a Hydroxide- Selective Column with a Reagent-Free Ion Chromatography System

Significance of the Topic

Municipal and bottled water providers face strict regulations on disinfection byproducts such as bromate, chlorite and chlorate, which pose health risks including potential carcinogenicity. Accurate, low-μg/L detection methods are essential for regulatory compliance and public health protection.

Objectives and Study Overview

• Implement and validate a reagent-free ion chromatography (RFIC) method using a hydroxide-selective Dionex IonPac AS19 column.
• Assess linearity, method detection limits (MDLs), precision, accuracy and matrix effects for trace oxyhalides and bromide.
• Demonstrate applicability to real municipal and bottled water samples.

Methodology

• Eluent Generation: Electrolytically generated KOH gradient (10–45 mM) on a Thermo Fisher Dionex ICS-2000 RFIC system.
• Detection: Suppressed conductivity with an ASRS ULTRA II suppressor in recycle mode.
• Sample Preparation: Filtration through 0.45 µm, addition of ethylenediamine preservative, optional dilution to avoid column overloading.
• Calibration and MDLs: Seven- to eight-point calibration; MDLs determined via replicate injections in reagent and simulated drinking water matrices.

Used Instrumentation

• Thermo Fisher Dionex ICS-2000 Reagent-Free IC system with EluGen EGC II KOH cartridge and CR-ATC trap column.
• Dionex IonPac AS19 analytical and AG19 guard columns.
• Dionex AS50 autosampler and Chromeleon Chromatography Workstation.

Key Results and Discussion

• Complete separation of 11 anions, including bromate and chloride, in under 30 minutes with baseline resolution.
• MDLs of 0.23–0.54 µg/L in reagent water; bromate MDL = 0.34 µg/L (≈70% lower than previous AS9-HC column).
• Excellent linearity (r² > 0.9995), retention time RSD < 0.03%, peak area RSD < 1.09%.
• Robust recoveries (95–110%) across municipal, bottled, groundwater and surface water samples.
• Tolerance up to ~150 ppm chloride and ~200 ppm sulfate at 250 µL injection; 500 µL injections feasible for low-ionic-strength samples.
• Detection of unexpected bromate in groundwater and several bottled waters, some near regulatory limits.

Benefits and Practical Applications

• Lower background conductivity and improved sensitivity by using ultrapure hydroxide eluent.
• Elimination of manual eluent preparation enhances automation, reproducibility and laboratory throughput.
• Method meets EPA and EU regulatory requirements for drinking water quality monitoring.

Future Trends and Potential Applications

• Coupling RFIC with mass spectrometry for enhanced selectivity and speciation.
• Integration of online sample preparation and portable IC systems for field monitoring.
• Extension to emerging oxyhalide contaminants and other environmental matrices.

Conclusion

The reagent-free ion chromatography method with a hydroxide-selective AS19 column offers a sensitive, precise and automated solution for trace determination of oxyhalides and bromide in drinking water, fulfilling stringent regulatory requirements and supporting high-throughput water quality analysis.

References

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