Retention models in ion chromatography: the role of side equilibria in ion-exchange chromatography of inorganic cations and anions

Analyte ions (inorganic cations and anions) as well as eluent constituents, can participate in various equilibria in the mobile phase. An effective separation of many metal cations is possible only in the presence of complexing agents forming kinetically labile complexes with the separated ions. The retention and separation of inorganic anions as well as metal complexes may be influenced by employing dissociation/protonation equilibria of analyte species and eluent ions. The role of these equilibria (acid-base and complex-forming) in ion-exchange chromatography is discussed in the present paper. The retention models can be utilized for an optimization of separation and also for an estimation of physical constants. (C) 1997 Elsevier Science B.V.