Determination of trace concentrations of oxyhalides and bromide in municipal and bottled waters

Significance of the Topic

Aims and Scope of the Study

Methodology and Instrumentation

• Eluent generation: 4.5 mM K₂CO₃/0.8 mM KHCO₃ prepared in situ by EGC 500 K₂CO₃ cartridge and EPM 500 pH modifier.
• Separation column: Dionex IonPac AS23-4µm analytical (4×250 mm) with AG23-4µm guard (4×50 mm).
• Suppression: AERS 500 carbonate suppressor, recycle mode, 32 mA current.
• Carbonate removal (optional): CRD 300 device in vacuum regeneration mode to strip CO₂ after suppression.
• Detection: suppressed conductivity at 25 °C; column at 30 °C; flow rate 1 mL/min; injection volume 250 µL.
• Sample preparation: 0.2 µm filtration, ethylenediamine (EDA) preservation, standard additions.

Main Results and Discussion

• Chromatographic resolution: AS23-4µm column achieved baseline separation of nine inorganic anions and DBPs; CRD 300 reduced background conductivity from ~18 µS to ~1.8 µS, enhancing signal-to-noise despite minor loss of resolution due to added dead volume.
• Linearity: coefficients of determination (r²) ≥ 0.9991 for chlorite, chlorate, bromide over 10–250 µg/L and bromate over 2–50 µg/L with CRD; similar performance without CRD over extended ranges.
• Detection limits: without CRD, MDLs ranged from 0.47 to 0.82 µg/L; with CRD, MDLs improved to 0.34–0.63 µg/L, all below regulatory thresholds.
• Accuracy and precision: recoveries in bottled and tap water spiked samples ranged from 85% to 115%; retention time RSDs < 0.1% and peak area RSDs < 2%.

Benefits and Practical Applications

• Automated reagent-free carbonate eluent generation streamlines method setup and eliminates manual buffer preparation.
• Sensitive quantification meets or exceeds regulatory requirements for drinking and bottled water monitoring without sample preconcentration.
• Robust operation supports routine QA/QC in water utilities and bottling facilities.

Future Trends and Potential Applications

• Integration of high-pressure IC platforms for shorter analysis times and increased throughput.
• Expansion to additional anion contaminants and emerging DBPs using advanced suppressors.
• Coupling with mass spectrometry for confirmatory identification of unknown DBPs.
• Development of portable or field-deployable IC systems for on-site water quality monitoring.

Conclusion

References

1. EPA. Drinking Water Treatment; EPA 810-F-99-013; U.S. EPA, 1999.
2. WHO. Disinfectants and Disinfection By-Products, Environmental Health Criteria 216; WHO, 2000.
3. Wagner HP et al. J. Chromatogr. A 1999, 850, 119–129.
4. U.S. EPA. National Primary Drinking Water Regulations: Disinfectants and Byproducts. Fed. Regist. 1998, 63, 69389–69476.
5. WHO. Background Document for Development of WHO Guidelines: Bromate in Drinking Water; WHO/SDE/WSH/05.08/78, 2005.
6. EU Directive 2003/40/EC on mineral water constituents and labeling.
7. Thermo Scientific Application Note 208: Determination of Bromate in Bottled Mineral Water; AN70405-EN, 2017.
8. Thermo Scientific IonPac AS23-4µm Column Manual; Man065711-EN.
9. Thermo Scientific Dionex VP Vacuum Pump Installation Instructions; Man065186-EN.
10. Thermo Scientific Dionex CRD 300 Carbonate Removal Device Product Manual; Man-CRD-300.
11. Thermo Scientific Application Update 203: Trace Oxyhalides and Bromide Using Compact IC; AU-203-AN72021-EN.
12. EPA Method 300.1: Determination of Inorganic Anions by Ion Chromatography; U.S. EPA, 1997.