Determination of Trace Concentrations of Disinfection Byproduct Anions and Bromide in Drinking Water Using Reagent-Free Ion Chromatography Followed by Postcolumn Addition of o-Dianisidine for Trace Bromate Analysis

Importance of the Topic

Drinking water disinfection byproducts such as bromate, chlorite, chlorate and bromide pose health risks and are strictly regulated worldwide. Monitoring trace-level anions ensures public safety and regulatory compliance.

Objectives and Study Overview

This study presents an improved ion chromatography method for simultaneous quantification of trace DBP anions in drinking water, combining reagent-free eluent generation and postcolumn derivatization to enhance bromate detection.

Methodology and Instrumentation

The method employs:

• Thermo Scientific Dionex ICS-2500 RFIC system with EG50 KOH eluent generator (10–45 mM gradient).
• Dionex IonPac AS19 analytical column with AG19 guard for hydroxide eluent.
• ASRS ULTRA II suppressor for conductivity detection of chlorite, chlorate and bromide.
• PC10 PCR module with o-dianisidine reagent, PCH-2 heater at 60 °C and 450 nm absorbance detection for bromate.

Main Results and Discussion

Calibration ranges: chlorite, chlorate, bromide 5–500 µg/L (r2>0.998); bromate conductivity 1–40 µg/L (r2=0.9997), visible 0.5–15 µg/L (r2=0.9996). MDLs: 0.26 µg/L (chlorite), 0.32 µg/L (bromate cond.), 0.14 µg/L (bromate vis.), 0.38 µg/L (chlorate), 0.52 µg/L (bromide). Recoveries in diverse water samples ranged 94–112% with RSD<4.5%. Postcolumn derivatization maintained conductivity sensitivity while lowering bromate quantitation limits.

Benefits and Practical Applications

Key benefits include:

• Lower background noise and detection limits using hydroxide eluent.
• Streamlined single-run analysis for multiple anions under EPA Method 317.0.
• No need for complex preconcentration to achieve sub-µg/L detection.

Future Trends and Potential Applications

Potential developments:

• Extension to other oxyhalides via tailored postcolumn reagents.
• Coupling with mass spectrometry for confirmation and further sensitivity.
• Real-time, automated monitoring in water treatment facilities.

Conclusion

The presented reagent-free IC method using a hydroxide-selective column and postcolumn o-dianisidine derivatization enables robust, sensitive, and selective measurement of trace bromate and related DBP anions, supporting effective water quality management.

References

EPA Method 317.0 (2000); Wagner et al., J. Chromatogr. A 1999, 850, 119; WHO 2000; Dionex Application Note 167.