Coupling of ion chromatography and inductively-coupled plasma mass spectrometry

Significance of the Topic

Ion chromatography coupled with inductively coupled plasma mass spectrometry (IC-ICP/MS) uniquely combines molecular separation of ionic species with ultra-trace elemental sensitivity. This hyphenated approach addresses critical needs for speciation analysis in environmental monitoring, water quality control, pharmaceutical testing, and food safety, where both the oxidation state and chemical binding of elements determine toxicity and bioavailability.

Objectives and Scope

The white paper reviews the coupling of high-performance IC to ICP/MS and illustrates its application across multiple elements (Cr, As, Hg, I, Gd, Se, Tl, Fe, Sb, Br, and organic chelants) in diverse matrices. Key aims are:

• To demonstrate reliable separation and quantification of oxidation states and species
• To outline method validation, including isotope-dilution techniques for species conversion correction
• To showcase practical workflows for routine and research laboratories

Methodology

Analytical strategies employ:

• Automated inline sample preparation and preconcentration (e.g., Metrohm Inline Sample Preparation, acetone matrix elimination)
• Anion- or cation-exchange columns optimized for target species (Metrosep, Hamilton PRP-X lines, microbore versions)
• Isocratic and gradient eluents (carbonate, nitrate, EDTA, ammonium acetate, or acidic buffers)
• Speciated isotope dilution mass spectrometry (SIDMS, EPA Method 6800) to correct for interconversion

Instrumentation

905 Professional IC Vario systems with MagIC Net software control are integrated with quadrupole ICP/MS detectors. Key features include automated eluent generation, remote synchronization, modular detection (conductivity, UV/VIS, amperometry), and compliance with GLP/FDA requirements.

Main Results and Discussion

Applications highlight rapid baseline separations in under 10 minutes and sub-ng/L detection limits:

• Chromium: Cr(III)/Cr(VI) speciation in soils, supplements, and consumer goods (EDTA eluents, SIDMS correction)
• Arsenic and selenium: simultaneous speciation in dietary supplements, fish tissues, and refinery waters (anion gradients, collision cell interference removal)
• Mercury: inorganic vs. methylmercury in biological and crude oil matrices (microwave-assisted extraction, SIDMS quantification)
• Iodinated contrast media: monitoring ozonation degradation to iodate in water
• Gadolinium chelates: assessing transmetallation during iron flocculation in wastewater
• Thallium: detection of dimethyl thallium at µg/L, speciation in seawater
• Iron: Fe(II)/Fe(III) speciation in environmental and beverage samples via dipicolinic acid complexation
• Antimony: Sb(III)/Sb(V) profiling in urban particulate matter
• Bromate: ultratrace determination in drinking water by microbore IC and ICP/MS
• Organic chelants (EDTA, DTPA, CDTA): indirect detection via metal complexes

Benefits and Practical Applications

IC-ICP/MS offers:

• High sensitivity and low detection limits (pg/L to ng/L)
• Automated, self-monitoring workflows minimizing operator error
• Wide dynamic range (>8 orders of magnitude)
• Multi-element and multi-species capability in single runs
• Compliance with regulatory standards (EPA, DIN, ASTM)

Future Trends and Opportunities

Advances in 2D chromatography, microfluidic IC, and high-resolution ICP/MS will expand capabilities for complex speciation, including nanoparticle and organometallic analyses. Integration with machine-learning algorithms promises automated data interpretation and predictive monitoring in real time. Further development of robust isotope-dilution protocols will enhance legal defensibility in environmental and forensic investigations.

Conclusion

Online coupling of IC and ICP/MS represents a versatile, robust platform for speciation analysis across diverse fields. By combining molecular separation with elemental detection and applying SIDMS corrections, laboratories can achieve accurate, sensitive, and high-throughput analyses essential for modern quality control, environmental compliance, and research.

References

Key standards and protocols include EPA Methods 321.8, 3052, 3060A, 6800; DIN EN 71-3; ASTM C1845; representative literature covers Herrmann T. 2006; Knöll J. 2013; Rahman G.M.M. et al. 2012; Reyes L.H. et al. 2009; Pfundstein P. et al. 2015; Künnemeyer J. et al. 2009; Wille A. et al. 2009; Marconi E. et al. 2011.