Analysis of Disinfection Byproducts by Ion Chromatography

Significance of Topic

The formation of disinfection byproducts (DBPs) during water treatment poses significant health risks, including carcinogenicity and reproductive toxicity. Accurate, sensitive and efficient analytical methods are essential to monitor regulated DBPs such as bromate, chlorite, chlorate and haloacetic acids (HAAs) in drinking water to ensure compliance with stringent standards and protect public health.

Objectives and Overview

This work aims to demonstrate the versatility and simplicity of modern ion chromatography (IC) platforms for DBP analysis through three approaches:

• Single-channel IC for routine anion quantification
• Two-dimensional IC (2-D IC) for enhanced selectivity and sensitivity
• IC coupled with mass spectrometry (IC-MS) for direct, confirmatory detection

The focus analytes include bromate, chlorite, chlorate, perchlorate and various haloacetic acids (HAA5, HAA9).

Methodology and Instrumentation

Key methodological elements encompass:

• Suppressed conductivity detection using Dionex IonPac columns (AS9-HC, AS19, AS23, AS24, AS26)
• Reagent-free eluent generation (RFIC) with hydroxide eluents via electrolytic generators
• Two-dimensional separations: large-bore first dimension for matrix removal and capillary second dimension for analyte focusing
• Optional post-column derivatization or IC-ICP/MS for ultralow detection of bromate

Major instruments:

• Thermo Scientific™ Dionex™ ICS-5000+ and ICS-6000+ HPIC systems
• Autosamplers, suppressors (ASRS™, AERS™), capillary concentrators (MAC-200)
• Electrolytic generators (EGC 500, capillary cartridges)
• Mass spectrometer interface for EPA Method 557 implementation

Main Results and Discussion

Bromate analysis by isocratic IC achieved detection limits down to 0.32 µg/L in simulated drinking water. Two-dimensional IC using a 4 mm AS19 first column and 0.4 mm AS20 second column delivered sub-µg/L sensitivity with sample loop volumes up to 1 mL. For HAA9 mixtures, the 2-D IC approach yielded Lowest Concentration Minimum Reporting Levels (LCMRLs) comparable or superior to EPA Method 557, e.g. MCAA at 0.085 µg/L vs 0.58 µg/L. Recoveries in reagent water, synthetic matrices and real surface and groundwater ranged from 87 % to 112 % with relative standard deviations ~0.5 %. Comparative analysis with EPA Method 552.3 (GC/ECD) showed excellent agreement for HAA5 compounds without lengthy derivatization steps.

Benefits and Practical Applications

The demonstrated IC workflows offer multiple advantages:

• Direct injection and automated eluent generation reduce manual sample preparation and derivatization (EPA 552.3)
• Enhanced selectivity through orthogonal column chemistries in 2-D IC minimizes matrix interferences
• High sensitivity rivaling mass spectrometry methods at lower operational cost
• Single-system implementation for multi-analyte DBP panels simplifies laboratory logistics

Applications span regulatory compliance monitoring, process control in water treatment plants and research on emerging DBPs.

Future Trends and Opportunities

Advancements likely to shape DBP analysis include:

• Broader regulatory acceptance of 2-D IC methods for HAAs and hexavalent chromium
• Integration of advanced detectors (MS/MS, ICP/MS) for confirmatory analysis and non-targeted screening
• Miniaturization via capillary IC for field-deployable, high-throughput monitoring
• Remote system control and predictive maintenance through digital connectivity (Unity™ Remote Services)

Conclusion

Modern ion chromatography, particularly two-dimensional IC, provides a robust, sensitive and streamlined alternative to traditional EPA methods for disinfection byproduct analysis. By eliminating extensive sample preparation and leveraging advanced system designs, laboratories can achieve regulatory compliance with improved efficiency and confidence.

Reference

No external literature references were provided.