IC-ICP/MS – with Metrohm

Importance of Speciation Analysis in Trace Element Determination

Speciation analysis is critical for understanding the true toxicity and environmental behavior of trace elements. Total element concentration often fails to distinguish between different oxidation states or chemical forms that vary widely in toxicity and mobility. By coupling ion chromatography with inductively coupled plasma mass spectrometry (IC-ICP/MS), analysts achieve both chemical selectivity and elemental sensitivity, enabling accurate determination of species such as Cr(III)/Cr(VI), arsenic species in food, and regulated anions like bromate.

Objectives and Study Overview

The primary aim of the described work is to demonstrate the benefits and workflow of integrating Metrohm ion chromatography systems with ICP/MS detection. The study outlines analytical goals including compliance with EPA method 321.8 for bromate, differentiation of chromium species, and speciation of arsenic in rice. Additionally, it highlights operational advantages such as prevention of matrix effects, low detection limits, and streamlined software control.

Methodology and Instrumentation

The methodology combines a Metrohm ion chromatograph with an ICP/MS detector (e.g., Metrohm IC coupled to PerkinElmer ICP/MS), controlled via Empower 3 CDS. Key chromatographic conditions for arsenic speciation include a Metrosep Carb 2 – 250/2.0 column, gradient eluent A (4 mmol/L ammonium bicarbonate) and B (4 mmol/L ammonium bicarbonate + 40 mmol/L ammonium nitrate) at pH 8.6, column temperature of 40 °C, 20 µL injection, and 0.2 mL/min flow rate. The ICP/MS was operated at 1550 W plasma power, 17 L/min plasma gas, 1 L/min auxiliary gas, 0.94 L/min nebulizer gas, and 0.1 s integration time.

Key Results and Discussion

The coupling enabled baseline separation of arsenic species in rice extract, demonstrating detection limits in the low ng/L range. Chromatographic separation effectively eliminated matrix interferences, while ICP/MS delivered element-specific quantification. The combined approach provided reliable speciation data required for accurate toxicity assessment and regulatory compliance.

Benefits and Practical Applications

• Correct toxicity assessment through species-specific quantification
• Prevention of matrix effects via selective chromatographic separation
• Lowest detection limits by adding high-sensitivity ICP/MS detection
• Single software control with comprehensive audit trails (Empower 3)
• Automatic sample preparation options (e.g., inline ultrafiltration, dialysis)
• Metal-free flow path for ultratrace analysis
• Robust hardware and proactive system monitoring

Future Trends and Applications

Emerging developments include expansion of inline automation for sample prep, integration with high-resolution mass spectrometry for isotope or molecular information, and application of chemometric and AI tools for real-time method optimization. Wider adoption of multi-element speciation in environmental, food safety, and pharmaceutical analysis is anticipated.

Conclusion

The Metrohm IC-ICP/MS combination offers a powerful platform for element-specific speciation with exceptional sensitivity and robustness. It addresses regulatory requirements, enhances data quality by mitigating matrix effects, and streamlines workflows through unified software control. This approach is poised to become the standard for routine speciation tasks in diverse analytical laboratories.

Reference

• Bischof, L. Use of the IC-ICP-MS and IC-ESI-MS coupling for the anion-chromatographic elemental species analysis of arsenic. Bachelor’s thesis, University of Marburg, 2017.
• Metrohm AG. White paper WP-008, Metrohm AG.