Analysis of inorganic anions in tap water according to EPA Method 300.1 using Ion Chromatography

Significance of the Topic

Ion chromatography with suppressed conductivity detection is a cornerstone technique for ensuring the safety and regulatory compliance of drinking water. Analysis of inorganic anions, including common species and disinfection by-products, is critical for monitoring water quality, protecting public health, and meeting stringent environmental standards.

Objectives and Study Overview

This study demonstrates the application of EPA Method 300.1 for determining ten inorganic anions in tap water using a suppressed ion chromatograph. Key aims include validating method detection limits, assessing linearity, evaluating recoveries and reproducibility, and illustrating practical tap water analysis.

Methodology and Instrumentation

The analytical procedure follows EPA Method 300.1, dividing targets into Part A (common anions) and Part B (inorganic disinfection by-products). Samples and standards contain a surrogate (dichloroacetic acid) and, for Part B, a preservation reagent (ethylenediamine). Chromatographic conditions are as follows:

• Column: Shodex SI-52 4E (250 mm × 4.0 mm, 5 µm) with Shodex SI-92G guard (10 mm × 4.6 mm, 9 µm)
• Mobile phase: 5.4 mmol/L sodium carbonate
• Flow rate: 0.8 mL/min; column temperature: 45 °C
• Injection volume: 50 µL for Part A; 200 µL for Part B
• Detection: suppressed conductivity using an electrodialytic suppressor and conductometric detector

Results and Discussion

Method detection limits (MDLs) for Part A ranged from 0.0008 to 0.0048 mg/L; for Part B from 0.53 to 1.33 µg/L. Calibration was linear across the tested ranges with relative response factors within acceptable limits. Analysis of tap water revealed measurable concentrations of fluoride, chloride, bromide, nitrate, and sulfate in Part A; most Part B analytes were below MDL except for bromide and chlorate. Recoveries from fortified tap water samples fell between 91% and 109%, with percent relative standard deviations below 2.6%, demonstrating accuracy and precision in line with EPA criteria.

Benefits and Practical Applications

• High sensitivity for trace anions in a single run of approximately 22 minutes
• Comprehensive analysis of both common inorganic anions and disinfection by-products
• Reuse of suppressor waste stream enhances environmental sustainability
• Suitable for routine water quality monitoring in research, QA/QC, and regulatory laboratories

Future Trends and Potential Applications

Advances may include coupling suppressed ion chromatography with mass spectrometry for enhanced selectivity, miniaturized flow cells for reduced reagent consumption, automated on‐line monitoring systems for real‐time water analysis, and expansion of detectable anion and cation species to address emerging contaminants.

Conclusion

The suppressed ion chromatography method on the Shimadzu Prominence IC system meets EPA Method 300.1 requirements, offering robust performance, rapid analysis, and eco‐friendly operation. It provides a reliable solution for routine inorganic anion monitoring in drinking water.

Used Instrumentation

• Shimadzu Prominence IC with electrodialytic suppressor (ICDSTM-40A) and CDD conductivity detector
• Shodex SI-52 4E analytical column and SI-92G guard column
• Shimadzu autosampler, high-pressure pump, and column oven

References

• EPA Method 300.1 Determination of inorganic anions in drinking water by ion chromatography, Revision 1.0