Analytical Sciences

Abstract − Analytical Sciences, 22(5), 715 (2006).

Interpretation of Solute Retention of Some Monovalent Inorganic Anions in Anion-Exchange Chromatography Using a Dicarboxylic Acid as an Eluent
Kaori TAMAYA, Sadaaki MORIGUCHI, Kunishige NAITO, and Shinsuke TAKEI
Department of Materials Science, Faculty of Engineering, Ibaraki University, Hitachi, Ibaraki 316-8511, Japan
In single-column anion-exchange chromatography, the retention volume of some monovalent inorganic anions (Cl-, Br-, NO3-, NCS- and NO2-) were observed as a function of the pH of a mobile phase at a fixed concentration of 2-phenylmalonic acid or 1,4-benzenediacetic acid used as an eluent. The experimental retention volume of such an anion was decreased with an increase in the pH of a mobile phase, and was able to be described by the following equation taking account of anion-exchange equilibria of a sample anion with a hydrogen dicarboxylate ion (HE-) and with a dicarboxylate ion (E2-): α1s/VR′[HE-] = 1/mTwKex1 + (2Ka2/mTw2Kex2)(VR′/α1s[H+]), where VR′, mT, w, Ka2, Kex1 and Kex2 are the adjusted retention volume of a given sample anion, the capacity for the anion-exchange of column packings and the weight of column packings packed into a separating column, the second acid-dissociation constant of the dicarboxylic acid used as an eluent, and equilibrium constants for the anion exchange of a sample anion with a monovalent hydrogen dicarboxylate ion and with a divalent dicarboxylate ion, respectively. The term α1s, defined as Kas/([H+] + Kas), where Kas is the acid-dissociation constant of HX, is the mole fraction of a sample anion, X-, and is equal to 1 when using a strong acid anion as a sample anion.