Determination of Bromate in Bottled Mineral Water Using the CRD 300 Carbonate Removal Device

Significance of the Topic

Bromate is a carcinogenic disinfection by-product formed when ozone reacts with bromide in drinking and bottled waters. Strict regulatory limits (10 µg/L by US EPA; 3 µg/L by the European Union for mineral and spring waters) demand highly sensitive analytical methods to ensure consumer safety and compliance.

Objectives and Study Overview

This application note evaluates the performance of the Thermo Scientific Dionex CRD 300 Carbonate Removal Device in combination with an IonPac AS23 column and suppressed conductivity detection. The goal was to determine bromate, chlorite, and chlorate in bottled mineral water at sub-µg/L levels and compare sensitivity and detection limits with and without carbonate removal.

Methodology and Instrumentation

The method employed either reagent-free carbonate eluent generation on a Dionex ICS-2000 system or manually prepared 4.5 mM Na₂CO₃/0.8 mM NaHCO₃ eluent. Carbonate removal was achieved post-suppression using the CRD 300 device in vacuum mode. Key instrumentation included:

• Dionex ICS-2000 Reagent-Free™ IC system with EGC II K₂CO₃ cartridge and EPM pH modifier
• Dionex IonPac AS23 analytical (4×250 mm) and AG23 guard (4×50 mm) columns
• Dionex ASRS™ 300 suppressed conductivity detector (25 mA, external water mode)
• Dionex CRD 300 Carbonate Removal Device (4 mm, vacuum mode)

Samples of bottled mountain spring water were directly injected (250 µL) with background spikes of fluoride, chloride, and sulfate. Calibration standards ranged from 10 to 40 µg/L for chlorite, bromate, and chlorate; MDL studies and spike recovery tests were performed accordingly.

Key Results and Discussion

Use of the CRD 300 device reduced the suppressed eluent background conductivity from ~18–19 µS to <1.5 µS, lowering noise from ~3 nS to ~0.3 nS. Method detection limits (MDLs) with carbonate removal were 0.75 µg/L for chlorite, 0.79 µg/L for bromate, and 0.68 µg/L for chlorate, compared to 1.86, 2.10, and 0.99 µg/L without. Calibration linearity remained >99.9% R² for both setups. Analysis of a bottled water sample revealed ~10.8 µg/L bromate and ~1.6 µg/L chlorate with CRD 300, whereas bromate appeared ~5.7 µg/L and chlorate was undetectable without, illustrating significant sensitivity loss without carbonate removal. Spike recovery exceeded 98% for all analytes with CRD 300 versus 85–97% without.

Benefits and Practical Applications

• Achieves sub-µg/L detection of bromate in bottled water via direct injection
• Reagent-free eluent generation enhances system reproducibility and convenience
• Post-suppression carbonate removal markedly improves signal-to-noise ratio
• Suitable for routine QA/QC and regulatory compliance in water analysis laboratories

Future Trends and Opportunities

Further integration of post-suppression carbonate removal with online eluent generation could streamline multi-anion analysis. Emerging two-dimensional IC techniques and coupling with mass spectrometry may extend this approach to ultra-trace determinations of a broader range of water contaminants.

Conclusion

Incorporating the Dionex CRD 300 Carbonate Removal Device with IonPac AS23 and suppressed conductivity detection significantly enhances sensitivity and lowers detection limits for bromate, chlorite, and chlorate in bottled mineral water. The method reliably meets stringent regulatory criteria and offers a robust, streamlined workflow for water quality laboratories.

References

1. U.S. EPA National Primary Drinking Water Regulations: Disinfectants and Disinfection Byproducts. Fed. Regist. 1998, 63(241), 69389–69476.
2. European Parliament and Council Directive 2003/40/EC on Natural Mineral Waters and Spring Waters, 2003.
3. Dionex (Thermo Scientific) Application Note 81: Ion Chromatographic Determination of Oxyhalides and Bromide, 1997.
4. Dionex (Thermo Scientific) AN 136: Determination of Disinfection By-Product Anions and Bromide with Postcolumn Reagent, 2004.
5. Dionex (Thermo Scientific) AN 149: Determination of Chlorite, Bromate, Bromide, and Chlorate with Online Postcolumn Reagent, 2003.
6. Dionex (Thermo Scientific) AN 167: Hydroxide Eluents for Trace Oxyhalides, 2004.
7. Dionex (Thermo Scientific) AN 168 and AN 171: Replacement of AS9-HC with AS19 for EPA Methods 317.0 and 326.0, 2005–2006.
8. Dionex (Thermo Scientific) Application Update 154: Isocratic Hydroxide Eluent for Bromate in Drinking and Mineral Water, 2006.
9. Dionex (Thermo Scientific) AN 184: Trace Bromate in Bottled Natural Mineral Waters, 2007.
10. Dionex (Thermo Scientific) AN 187: Two-Dimensional IC for Sub-µg/L Bromate by IC-MS/MS, 2007.