Extended thermodynamic approach to ion-interaction chromatography for high surface potential: use of potential approximation for simplified retention equations

The chromatographic behaviour of charged analytes in ion interaction chromatography (IIC) has been investigated theoretically. A potential approximation for high surface potential was used to obtain simplified retention equations that are able to model analyte retention as a function of both the mobile and stationary phase concentrations of the ion-interaction reagent (IIR). The main advantage of using this potential approximation is that it allows calculation of the surface potential, without needing detailed information on physical and chemical properties of the mobile phase. Retention equations of previous thermodynamic retention models can be viewed as limiting cases of the present theory. One of the most reliable data sets concerning the retention behaviour of charged substances in IIC, obtained at high surface potential, was used to test the new retention equations.