Determination of inorganic anions by electrostatic ion chromatography witha cation exchange column as a pre-column for conversion of the cations into a common species

The problem of "multiple" distribution of the analyte ions encountered in t he separation of inorganic ions by electrostatic ion chromatography (EIC) w as overcome. EIC is a new type of ion chromatography (IC) where zwitterioni c molecules are used as the stationary phase and pure water serves as the m obile phase. Both ions and polar organic compounds can be separated by EIC and the simultaneous electrostatic attraction-repulsion interactions betwee n the positive-negative charges (or polarities) of the analytes and the sta tionary phase are considered to be the main mechanisms for the separation. In the analysis of inorganic ions by EIC, each species of the cation and/or anion was distributed to all species of the counterion and co-eluted as pa iring ions. To avoid such "multiple" distribution of the analyte ions, the analyte cations were converted into a common species of either Na+ or Mg2by using conventional cation exchange columns as the pre-column. The analyte anions were excellently separated by this method and, furthermo re, "exclusive" distribution (single peak per one species of anion) was obt ained. Real sample (underground water) was analyzed in duplicate using a co nventional anion-exchange IC and this proposed method and identical results were obtained.