Analysis of Dissolved Hexavalent Chromium

Significance of the Topic

Hexavalent chromium is a widespread pollutant in industrial wastewaters and poses serious health and environmental risks. Reliable detection at low levels is essential for compliance with environmental regulations and protection of ecosystems and public health.

Objective and Overview of the Study

This application note demonstrates the performance of an ion chromatography method using the Shim-pack IC-SA2 column to quantify dissolved Cr(VI) in water samples. It follows EPA method 218.6 principles and incorporates post-column derivatization to enhance detection sensitivity.

Methods and Instrumentation

The separation of Cr(VI) was achieved on a 250 mm × 4.0 mm Shim-pack IC-SA2 analytical column with a matching guard column. The mobile phase consisted of 25 mM ammonium sulfate and 10 mM ammonium hydroxide at a flow rate of 1.5 mL/min. Post-column reagents included 2 mM diphenylcarbazide in 10 percent methanol with 0.5 mM sulfuric acid delivered at 0.5 mL/min. The column was maintained at 40 °C, and sample injections of 250 µL were used. Detection was performed using UV-VIS at 530 nm following color development in a 10 m reaction coil.

Main Results and Discussion

The method produced sharp Cr(VI) peaks with high reproducibility. Calibration curves were linear over the regulatory range, achieving low detection limits suitable for trace analysis. Recovery studies in spiked wastewater samples demonstrated accuracy within acceptable limits. The post-column derivatization provided stable absorbance signals and minimal background interference.

Benefits and Practical Applications

The described procedure offers a robust and sensitive approach for routine monitoring of hexavalent chromium in environmental and industrial effluents. It supports regulatory compliance and quality control in laboratories handling wastewater analysis.

Future Trends and Potential Applications

Advances may include integration with automated sample preparation systems and coupling to mass spectrometric detectors for simultaneous multi-analyte screening. Miniaturization and on-site testing devices could further streamline monitoring tasks.

Conclusion

The Shim-pack IC-SA2 based ion chromatography method with post-column derivatization reliably quantifies Cr(VI) at trace levels, ensuring accurate and reproducible results for environmental monitoring.

Reference

• Application News an_01-00380 (JP, ENG), Shimadzu Corporation, First Edition August 2023.