Determination of Trace Concentrations of Chlorite, Bromate, and Chlorate in Bottled Natural Mineral Waters

Significance of the Topic

Bottled natural mineral water consumption has risen significantly, driving the need for rigorous quality control to ensure safety. Disinfection methods like ozonation effectively remove pathogens but can generate harmful byproducts such as chlorite, bromate, and chlorate. Bromate is recognized as a potential human carcinogen at low microgram-per-liter levels. Regulatory bodies, including the US EPA, FDA, European Commission, and WHO, limit bromate in drinking water to 3–10 µg/L. Accurate trace analysis of these anions in bottled waters is thus essential for compliance and consumer protection.

Objectives and Overview of the Study

This study compares two ion chromatography approaches for simultaneous determination of chlorite, bromate, and chlorate at trace levels in bottled natural mineral waters. One method utilizes a hydroxide-selective IonPac AS19 column with electrolytic KOH eluent, and the other employs an IonPac AS23 column with on-line generated carbonate/bicarbonate eluent modified by an electrolytic pH modifier. Key performance indicators include calibration linearity, detection limits, precision, and recovery in real water matrices.

Methodology

Three European natural mineral waters with total dissolved solids ranging from 136 to 2359 mg/L were analyzed. Samples were vacuum-degassed or diluted to control high bicarbonate or sulfate content. Calibration standards were prepared from primary stocks to cover regulatory concentration ranges. Two eluent systems were generated on-line: a KOH gradient for AS19 and a 4.5 mM carbonate/0.8 mM bicarbonate isocratic eluent for AS23.

Used Instrumentation

• Thermo Scientific Dionex ICS-2000 (or ICS-2100) RFIC system
• Dionex EluGen II KOH and K₂CO₃ cartridges with EPM pH modifier
• CR-ATC continuously regenerated anion trap suppressor
• IonPac AS19 4×250 mm and AG19 guard columns
• IonPac AS23 4×250 mm and AG23 guard columns
• ASRS ULTRA II suppressor in recycle or external water mode
• Dionex AS autosampler
• Dionex Chromeleon chromatography data system

Main Results and Discussion

Both methods delivered excellent calibration linearity (r² > 0.999). The AS19 hydroxide method achieved MDLs of 0.18 µg/L for chlorite, 0.31 µg/L for bromate, and 0.28 µg/L for chlorate. The AS23 carbonate method achieved MDLs of 1.02, 1.63, and 2.05 µg/L, respectively. Superior sensitivity for bromate with the AS19 approach meets stringent European (3 µg/L) and US (10 µg/L) regulatory limits. Recovery studies in three bottled waters spiked with 5 µg/L bromate and 10 µg/L chlorite/chlorate yielded 86–97% (AS19) and 84–111% (AS23).

Benefits and Practical Applications

The AS19 hydroxide-based method provides enhanced sensitivity for trace bromate, ensuring compliance with global drinking water standards. On-line, reagent-free eluent generation reduces manual preparation, minimizes variability, and increases throughput. Both methods achieve effective separation of DBP anions from common inorganic anions, supporting routine quality control in water production and environmental monitoring.

Future Trends and Opportunities

Emerging advancements may include coupling IC with mass spectrometry to improve specificity and detection limits. Automation and multi-analyte screening will streamline workflows. Novel stationary phases and eluent technologies could shorten analysis times and enhance resolution. Portable IC systems may enable on-site, real-time monitoring of DBPs in water supplies.

Conclusion

Comparative evaluation of IonPac AS19 with hydroxide eluent and AS23 with carbonate/bicarbonate eluent demonstrates that the AS19 method delivers superior sensitivity for trace bromate in mineral waters. Both protocols provide accurate, precise quantitation of chlorite, bromate, and chlorate, supporting compliance with stringent regulations. Reagent-free electrolytic eluent generation further enhances laboratory efficiency and reproducibility, making these approaches ideal for routine DBP analysis in bottled water.

Reference

1. EPA Method 300.1: Determination of Inorganic Anions in Drinking Water by Ion Chromatography. US EPA, 1997.
2. EPA Method 317.0: Determination of Inorganic Oxyhalide DBPs with Postcolumn Reagent. US EPA, 2001.
3. EPA Method 326.0: Ion Chromatography with Acidified Postcolumn Reagent for Bromate. US EPA, 2001.
4. WHO: Bromate in Drinking Water—Background for WHO Guidelines, 2005.
5. European Parliament Directive 2003/40/EC on Natural Mineral Waters, 2003.
6. US EPA Stage 2 Disinfectants/DBP Rule, 2006.