A multifunctional dual membrane electrodialytic eluent generator for capillary ion chromatography

A multifunctional electrodialytic generator (EDG) for capillary ion chromatography (CIC) is described. The same device can generate acidic, basic or saline eluents. Two oppositely charged ion exchange beads are used to fabricate the EDG; the dual ion exchanger configuration ensures the production of gas-free eluent, obviating the need of a gas removal device used with single ion exchanger EDG's. The ability of the same EDG to produce different eluents is governed solely by the choice of the respective feed solutions; this is presently demonstrated by generation of diverse eluents such as Na2CO3/NaHCO3, CH3SO3H, and KNO3. The EDG is implemented simply in a commercial cross fitting and has been tested up pressures to 2000 psi. Under typical operating conditions, the zero current concentration (open circuit penetration, OCP) is negligible. The generated eluent concentration linearly increases with applied current with a slope that is essentially Faradaic. The device permits both isocratic and gradient operation with good reproducibility, as demonstrated by the analysis of anions using HCO3−/CO32− EDG.