ELECTROSTATIC ION CHROMATOGRAPHY .2. PARTITIONING BEHAVIORS OF ANALYTE CATIONS AND ANIONS

Partitioning behaviors of analyte cations and anions in ''electrostati c ion chromatography (electrostatic IC)'' were investigated. Detectors of ICP-AES (inductively coupled plasma atomic emission spectrometry), UV absorption, and conductivity were connected on-line to the electro static IC and used for the selective detection of cations, anions, and ''ion-pairing-like forms'' (both cations and anions), respectively. W hen a mixed electrolytic aqueous solution containing cations A, C, ... , Y, and anions B, D, ..., Z, was passed through the electrostatic IC column, the analyte ions, which dissociated from the original salts AB , CD, ..., and YZ, were each redistributed and forced into a new state . This new state was termed an ion-pairing-like form because of the si multaneous electrostatic attraction and repulsion interactions. The sa me species of anion or cation are found in more than one ion-pairing-l ike form; however, they occur in different volumes. What is more, each ion-pairing-like form has a different priority of formation. Born's e quation was used to evaluate that priority. Retention time of the ion- pairing-like form was dependent on the species of the anion and the ch arge of the cation. All ion-pairing-like forms can be simultaneously s eparated with the exception of those having the same anion species as well as the same cation charge. Ion chromatography using a strong/stro ng positive/negative charged zwitterionic stationary phase with pure w ater as the mobile phase was termed electrostatic ion chromatography.( 1)