Analysis of Anions by Ion Chromatography

Importance of the Topic

Ion chromatography is fundamental for water quality, environmental monitoring, industrial process control, and food safety, as it provides accurate quantification of anions critical to these fields.

Objectives and Study Overview

This application note demonstrates the separation and detection of seven common inorganic anions using the Shim-pack IC-SA2 column. It aims to validate a rapid, reliable method for routine analysis of fluoride, chloride, nitrite, bromide, nitrate, phosphate, and sulfate in aqueous samples.

Methodology and Chromatographic Conditions

The separation was achieved by isocratic elution with a mobile phase composed of 0.6 mmol/L sodium carbonate and 12.0 mmol/L sodium hydrogen carbonate at a flow rate of 1.0 mL/min. The column temperature was maintained at 30 °C and a 50 µL sample injection volume was employed. Conductivity detection allowed for sensitive measurement of anion concentrations.

Used Instrumentation

• Ion chromatography system: Shimadzu HIC-ESP
• Analytical column: Shim-pack IC-SA2 (250 mm × 4.0 mm I.D., 9 µm)
• Guard column: Shim-pack IC-SA2(G) (10 mm × 4.6 mm I.D., 9 µm)
• Detector: Conductivity detector
• Sample vial: 4 mL polypropylene vial

Main Results and Discussion

The method achieved baseline separation of seven anions within 20 minutes. Representative retention times for 1.0 mg/L fluoride and chloride were approximately 3 and 4 minutes, respectively, while larger ions such as phosphate and sulfate eluted later. Sensitivity and resolution were sufficient for low mg/L level quantification. The conductivity signal provided distinct peaks with minimal overlap, demonstrating the column performance under the selected eluent conditions.

Benefits and Practical Applications

• Rapid analysis: complete separation in under 20 minutes maximizes sample throughput.
• Sensitivity and selectivity: ideal for environmental water analysis, QA/QC in chemical manufacturing, and food and beverage monitoring.
• Robustness: stable baseline and reproducible retention times ensure reliable long-term operation.

Future Trends and Potential Applications

With ongoing advancements in column chemistry and detector technologies, future IC methods will likely achieve faster run times and lower detection limits. Integration with mass spectrometry could extend capabilities to trace level analysis of anionic contaminants. Automation and inline sampling will further streamline environmental and industrial monitoring workflows.

Conclusion

The Shim-pack IC-SA2 column combined with a carbonate/bicarbonate eluent and conductivity detection offers a robust, efficient solution for comprehensive anion analysis. The method balances speed, resolution, and sensitivity, making it suitable for a wide range of routine applications in analytical laboratories.

Reference

Shimadzu Application News 01-00252 (JP), Analysis of Anions by Ion Chromatography, First Edition: December 2021.