SIMULTANEOUS SEPARATION OF INORGANIC CATIONS AND ANIONS BY ION CHROMATOGRAPHY USING A SINGLE-COLUMN COATED WITH WEAK STRONG-CHARGED ZWITTERIONIC BILE-SALT MICELLES/

A single reversed-phase ODS (octadecyl silica) column coated with taur ine-conjugated bile salt micelles has been investigated for simultaneo us separation of inorganic cations and anions. Under acidic conditions in the separation column, taurine conjugated bile salts are protonate d; therefore, the stationary phase coated with taurine-conjugated bile micelles exists as a ''weak/strong''-charged zwitterionic stationary phase (H+ and SO3-). The weak/strong-charged zwitterionic stationary p hase provides a new retention mechanism which is different from conven tional ion chromatography in that both positive and negative charges a re close together in a single molecule, resulting in simultaneous elec trostatic attraction and repulsion of the analyte ions. Also, the stro nger negative charge (sulfonate) of the stationary phase works as a ca tion-exchange site at the same time. The combined effects of cation-ex change and simultaneous electrostatic repulsion/attraction interaction s were successfully used in ion chromatography for the simultaneous se paration of inorganic cations and anions.