A gas-free electrodialytic pH modifier for ion chromatography

Area of Science:

• Analytical Chemistry
• Separation Science
• Electrochemistry

Background:

• Ion chromatography (IC) commonly uses carbonate eluents.
• Precise control over eluent composition is crucial for optimizing IC separations.
• Existing methods for eluent modification can be complex or introduce unwanted byproducts.

Purpose of the Study:

• To introduce a novel gas-free electrodialytic device for real-time pH modification of carbonate eluents.
• To demonstrate the device's capability in converting potassium carbonate (K2CO3) to potassium bicarbonate (KHCO3) for IC applications.
• To evaluate the efficiency, reproducibility, and performance of the developed electrodialytic modifier.

Main Methods:

• A sandwich-configured electrodialytic cell with stacked cation exchange membranes (sCEM) and a bipolar membrane plus stacked anion exchange membranes (BPM-sAEM).
• Electrodialysis was applied to a potassium carbonate eluent flowing through a central channel, with electrodes in adjacent regenerant chambers.
• Current was controlled to induce ion migration and water splitting for eluent modification.

Main Results:

• The device successfully modified a 10 mM K2CO3 eluent to 10 mM KHCO3 with high Faradaic efficiency (approximately 92%).
• The system demonstrated excellent reproducibility, with retention time relative standard deviation (RSD) below 0.43% and peak area RSD below 0.93%.
• The electrodialytic pH modifier operates without gas generation, simplifying its integration into IC systems.

Conclusions:

• The developed gas-free electrodialytic pH modifier offers a robust and efficient method for online eluent manipulation in ion chromatography.
• This technology allows for precise control over carbonate/bicarbonate ratios, potentially improving chromatographic resolution and sensitivity.
• The device's high reproducibility and operational simplicity make it a promising tool for advanced IC applications.