Simultaneous analysis of common inorganic species in seawater samples by ion-exclusion/cation-exchange chromatography

Ion-exclusion/cation-exchange chromatography (IEC/CEC), which consists of a cation-exchange resin column and a weak acidic eluent, was used for the simultaneous analysis of common inorganic species (SO42-, Cl-, Na+, K+, Mg2+ and Ca2+) in seawater. When conventional IEC/CEC is applied to seawater containing high concentrations of Na+ or Cl-, a poor resolution between SO42- and C- was obtained. Therefore, the cation-exchange resin packed to the separation column was reconsidered in terms of the kind of carrier and the magnitude of the exchange-capacity. In this study, the optimal column was a polymethacrylate-based weakly acidic cation-exchange resin with 0.15 meq./mL-capacity. This could provide good resolutions of anions by an increase of the penetration effect to the resin phase as well as those cations by the cation-exchange effect. The simultaneous separation and determination was achieved in 20 min. The relative standard deviations of the peak areas in consecutive runs (n = 10) ranged from 0.2% to 2.5%.