Measuring inorganic cations and amines with ion chromatography mass spectrometry (IC-MS)

Significance of the Topic

Ion chromatography coupled with mass spectrometry (IC-MS) merges two proven techniques to deliver high sensitivity, multi-analyte capability, and robust peak confirmation in a single analytical run. This approach addresses growing demands in environmental monitoring, food safety, petrochemical process control, and quality assurance by streamlining workflows, minimizing manual steps, and ensuring data integrity.

Objectives and Study Overview

The white paper demonstrates IC-MS applications for quantifying inorganic cations (alkali and alkaline earth metals) and various amines (biogenic amines, ethanolamines, methylamines) in diverse matrices. Key aims include:

• Evaluating biogenic amine determination in foods and beverages
• Assessing ethanolamine and methylamine analysis in industrial process water
• Measuring inorganic cations as bare ions and acetone adducts in water samples

Methodology and Instrumentation

A fully automated IC-MS system was controlled by a single software platform (Metrohm drivers for Waters Empower and Agilent OpenLab). Inline sample preparation options (ultrafiltration, dialysis) reduced manual steps. Separation used Metrosep C Supp 1 and C4 columns with oxalic acid-based eluents (suppressed or non-suppressed conductivity). A single quadrupole ESI-MS recorded selected ion traces in parallel with conductivity signals. For alkali metals, acetone was added to the eluent to form stable adducts and enhance sensitivity.

Main Results and Discussion

Biogenic amines (eight compounds) were separated on a C Supp 1 column with an oxalic acid/methanol gradient. Detection limits reached low µg/L with 2% RSD at 1 µg/L putrescine. Ethanolamines and methylamines in process water achieved sub-µg/L detection using non-suppressed IC-MS and selective ion monitoring. Inorganic cations (K, Rb, Cs, Ca, Sr, Ba) were quantified as bare ions by simultaneous conductivity and MS detection at 0.5 mg/L levels. Lithium and sodium adducts formed with acetone enabled detection down to 10 µg/L.

Benefits and Practical Applications

• Comprehensive multi-analyte runs reduce instrumentation and sample handling
• Parallel conductivity and MS detection ensure accurate peak identification and quantitation
• Inline sample preparation enhances reproducibility and instrument protection
• Adaptable to food safety, environmental, and industrial matrices

Future Trends and Possibilities

Advances may include expanded inline prep modules, novel suppressor technologies for broader eluent compatibility, and integration with data-science tools for automated peak deconvolution. Emerging applications could cover isotope-specific speciation studies, mobile IC-MS platforms for on-site monitoring, and greener eluent systems.

Conclusion

IC-MS offers a powerful, versatile, and efficient solution for trace analysis of inorganic cations and amines across a wide range of matrices. Its automation, dual-detector confirmation, and low detection limits make it a valuable tool in modern analytical laboratories.

References

1. Michalski R., Ed. IC-MS and IC-ICP-MS in Environmental Research; John Wiley & Sons, 2016
2. Sánchez J., Ruiz-Capillas C. Optimizing Chromatographic Analysis of Biogenic Amines in Fish. Eur Food Res Technol, 2011, 234, 285–294
3. Buňka F. et al. Biogenic Amines Content in Selected Wines During Winemaking. J Microbiol Biotechnol Food Sci, 2012, 1(4), 785–793
4. Dashti S. et al. Sensitivity Analysis for Optimum Amine Gas Sweetening. Asia-Pac J Chem Eng, 2015, 10(5), 709–715