Influence of acidic eluent for retention behaviors of common anions and cations by ion-exclusion/cation-exchange chromatography on a weakly acidic cation-exchange resin in the H+-form

Influence of acidic eluent on retention behaviors of common anions and cations by ion-exclusion/cation-exchange chromatography (ion-exclusion/CEC) were investigated on a weakly acidic cation-exchange resin in the H+-form with conductivity. Sensitivities of analyte ions, especially weak acid anions (F− and HCOO−), were affected with degree of background conductivity level with pKa1 (first dissociation constant) of acid in eluent. The retention behaviors of anions and cations were related to that of elution dip induced after eluting acid to separation column and injecting analyte sample. These results were largely dependent on the natures of acid as eluent. Through this study, succinic acid as the eluent was suitable for simultaneous separation of strong acid anions (SO42−, Cl−, NO3− and I−), weak acid anions (F−, HCOO− and CH3COO−), and cations (Na+, K+, NH4+, Mg2+ and Ca2+). The separation was achieved in 20 min under the optimum eluent condition, 20 mM succinic acid/2 mM 18-crown-6. Detection limits at S/N = 3 ranged from 0.10 to 0.51 μM for strong acid anions, 0.20 to 5.04 μM for weak acid anions and 0.75 to 1.72 μM for cations. The relative standard deviations of peak areas in the repeated chromatographic runs (n = 10) were in the range of 1.1–2.9% for anions and 1.8–4.5% for cations. This method was successfully applied to hot spring water containing strong acid anions, weak acid anions and cations, with satisfactory results.