Speciation of Cr(III) and Cr(VI) on Metrosep Carb 2 - 100/2.0 applying IC-ICP/MS

Significance of the Topic

Accurate differentiation between trivalent chromium (Cr(III)) and highly toxic hexavalent chromium (Cr(VI)) is crucial for environmental monitoring, regulatory compliance, and health protection. Speciation analysis ensures reliable assessment of chromium contamination in water and industrial effluents and supports informed decision-making in environmental and quality control laboratories.

Objectives and Study Overview

This application note demonstrates a rapid and sensitive ion chromatography–inductively coupled plasma mass spectrometry (IC-ICP/MS) method for separating and quantifying Cr(III) and Cr(VI). The study aims to exploit a Metrosep Carb 2 – 100/2.0 microbore column to achieve clear resolution of the Cr(III)-EDTA complex and chromate anion, enabling direct coupling to ICP-MS without flow splitting.

Methodology

The separation is performed on a Metrosep Carb 2 – 100/2.0 column with a guard column at ambient temperature. A 100 mmol/L ammonium nitrate eluent at pH 9 (adjusted with NH₄OH) carries the analytes at 0.2 mL/min. Samples are complexed with 20 µmol/L EDTA to convert Cr(III) into a stable anionic species. A 20 µL injection volume is used, and total run time is 10 minutes. ICP-MS detection monitors mass 52 amu in helium collision‐cell mode to minimize interferences.

Used Instrumentation

• 940 Professional IC Vario ONE (Metrohm) with Professional Sample Processor
• Agilent 7500ce ICP-MS

Main Results and Discussion

Calibration standards ranging from 0.2 to 4.0 µg/L for Cr(III) and Cr(VI) exhibited excellent linearity. Limits of detection were determined at 0.11 µg/L for Cr(III) and 0.01 µg/L for Cr(VI). Chromatograms show baseline separation of the Cr(III)-EDTA complex prior to the Cr(VI) peak, with sharp peak shapes and reproducible retention times. The microbore format eliminated the need for flow splitting, preserving sensitivity.

Benefits and Practical Applications

• High sensitivity for trace chromium speciation in environmental and industrial samples
• Direct IC-ICP/MS coupling without splitter simplifies system setup and reduces sample loss
• Short analysis time (10 min) supports high sample throughput
• Robust separation under isocratic conditions minimizes method complexity

Future Trends and Potential Applications

Advances may include miniaturized chromatography modules for field deployment and integration with automated sample preparation to further boost throughput. The approach can be adapted for other redox‐sensitive metals and expanded to multi‐element speciation workflows in environmental and clinical matrices.

Conclusion

The described IC-ICP/MS method employing a Metrosep Carb 2 microbore column delivers efficient, reliable speciation of Cr(III) and Cr(VI) with low detection limits and high throughput. Its ease of use and direct coupling capabilities make it an attractive choice for routine laboratory analysis of chromium contamination.

Reference

Metrohm IC Application Note M–13: Speciation of Cr(III) and Cr(VI) on Metrosep Carb 2 – 100/2.0 by IC-ICP/MS