Extended thermodynamic approach to ion interaction chromatography

The chromatographic behavior of charged analytes in ion interaction chromat ography (IIC) is theoretically investigated, The chemical modifications of the stationary and mobile phases in the presence of ion interaction reagent (IIR) are theoretically shown to change the partition coefficient for char ged molecules. The most reliable literature experimental results concerning retention behavior of charged molecules in IIC were used to test the new t heory. Retention equations are compared with those that can be obtained fro m the most important retention models in IIC. The present exhaustive retent ion model, which is well-founded in physical chemistry, goes further than t he previous ones whose retention equations can be viewed as limiting cases of the present theory. The present extended thermodynamic approach reduces to stoichiometric or electrostatic retention models if the surface potentia l or pairing equilibria are respectively neglected, Moreover, it is able to quantitatively explain experimental evidences that cannot be rationalized by the existing retention models.