Anion Determinations in Municipal Drinking Water Samples Using EPA Method 300.1 (A) on an Integrated IC System

Importance of Anion Determination in Drinking Water

Anions such as fluoride, nitrite, and nitrate are regulated under EPA primary drinking water standards due to health risks including fluorosis and methemoglobinemia. Chloride and sulfate are monitored for aesthetic quality. Ion chromatography provides a reliable approach for compliance testing under EPA Method 300.1(A).

Study Objectives and Overview

This application update demonstrates EPA Method 300.1(A) using a high-capacity Dionex IonPac AS22 column on integrated IC systems (ICS-1100 or ICS-1600). Key aims include comparing performance with the earlier AS14 column, optimizing manual carbonate/bicarbonate eluent preparation, and evaluating method sensitivity, reproducibility, and accuracy in municipal and surface water samples.

Methodology and Instrumentation

• Instrumentation
  • Dionex ICS-1100 or ICS-1600 integrated ion chromatography system
  • Dionex AS-DV autosampler
  • Chromeleon CDS version 7.2
  • Dionex IonPac AG22 guard column (4×50 mm) and AS22 analytical column (4×250 mm)
  • Dionex AERS 500 electrolytically regenerated suppressor
• Eluent preparation: 4.5 mM sodium carbonate and 1.4 mM sodium bicarbonate from concentrate, manually prepared and degassed
• Operating conditions: flow rate 1.2 mL/min, column temperature 30 °C, injection volume 5 µL, suppressed conductivity detection in recycle mode at 31 mA
• Sample preparation: 0.2 µm filtration for surface waters, direct injection for municipal waters

Results and Discussion

• Column comparison: AS22 offers threefold higher capacity (210 µeq vs 65 µeq) and reduces run time by 2 min compared to AS14, while maintaining selectivity and improving acetate/fluoride separation.
• Separation performance: eight common anions eluted within 12 min on AS22 versus 14 min on AS14 at identical conditions.
• Linearity and detection limits: calibration linearity r2>0.999 over optimized ranges; MDLs from 0.042 mg/L (fluoride) to 0.763 mg/L (phosphate) for direct injection of undiluted samples.
• Reproducibility: retention time RSD ≤0.54% and peak area RSD ≤1.2% over four days.
• Sample analysis: municipal waters from California cities and surface waters (Lake Tahoe and Whitewater River) yielded expected anion profiles with high accuracy and precision.
• Recovery studies: 96–106% in laboratory fortified blank and 90–101% in fortified water samples.

Benefits and Practical Applications

• Efficient compliance testing with cost-effective manual eluent preparation.
• Higher throughput due to reduced analysis time and increased column capacity.
• Robust performance suitable for routine drinking water monitoring under EPA regulations.

Future Trends and Potential Uses

• Adoption of automated eluent generation to minimize manual variability.
• Extension to gradient separations for analysis of a broader range of ions.
• Development of advanced column chemistries for enhanced selectivity and longevity.

Conclusion

The Dionex IonPac AS22 column on integrated IC systems effectively meets EPA Method 300.1(A) requirements, delivering faster, precise, and reproducible determination of inorganic anions in drinking water. This method supports reliable routine compliance monitoring.

References

1. EPA National Primary Drinking Water Regulations 40 CFR Part 141
2. EPA Method 300.0 Determination of Inorganic Anions in Water by Ion Chromatography
3. Thermo Fisher Scientific, Application Note 133: Determination of Inorganic Anions in Drinking Water by IC
4. Thermo Fisher Scientific, Application Note 154: Determination of Inorganic Anions in Environmental Waters
5. Thermo Fisher Scientific, Application Note 175: Determination of Sulfate and Chloride in Ethanol by IC
6. Thermo Fisher Scientific, Dionex IonPac AS22 Column Product Manual
7. Thermo Fisher Scientific, Dionex AERS 500 Suppressor Product Manual