Determination of Effective Capacities of Ion-Exchangeable Materials by Measuring the Equilibrium Conductivity

Abstract

The effective ion-exchange capacities of ion-exchange materials were determined by measuring the change in the equilibrium conductivity of a column packed with analyte. The developed instrumental method can provide effective ion-exchange capacities for both cation and anion exchangers with simple operations. The cation-exchange capacity of a weak-acid cation-exchange resin (TSKgel SuperIC-Cation column) depended on the conditioning pH and the molar concentration of the conditioning agent. Plots of effective cation-exchange capacities over the conditioning pH exhibited three inflection points, suggesting the presence of two carboxy groups and one phenolic OH group in the resin, probably due to the inherent base polymer. This method was applied to several commercial analytical columns for ion chromatography, and could provide scientifically useful results for characterizing the resin properties.

Fast and Efficient Separation and Determination of UV-absorbing Amino Acids, Nucleobases, and Creatinine Using a Carboxy-functionalized Cation-exchange Column

“…whole capacity by cation-exchangeable functional groups, in weak-acid cation-exchange resins is in general very high, e.g., exceeding 1 mol/L-resin, the working cation-exchange sites under a weakly acidic pH condition on cation chromatography are thought to be very small, e.g., in the order of mmol/L-resin or less. We recently have developed a capacity analyzing system, 24 which looks like an ion-chromatography system without sample injector, and also have improved the equilibration buffer system. 9 This can provide a dynamic capacity curve, that is, plots of the changes in dynamic exchange capacities (DECs) over the column effluent pH after equilibration with several buffer solutions.…”

“…9 This can provide a dynamic capacity curve, that is, plots of the changes in dynamic exchange capacities (DECs) over the column effluent pH after equilibration with several buffer solutions. The mole flux of H + required for exchanging from Na + -form to H + -form of the cation-exchange resin (molar concentration × time × flow-rate) can correspond to the dynamic cation-exchange capacity 24 under the buffer pH conditions subjected. The prefixed term dynamic implies the effective capacity on the chromatography process.…”