Thermodynamic and conceptual modeling of component interactions in liquid chromatography : application to reversed-phase ion-interaction and normal phase systems

A novel pulse technique in which ion-interaction reagent is added to the column in pulses rather than constantly present in the eluent is given. A method for optimizing a separation with the pulse technique is demonstrated. A general model based upon interactions among eluent and sample components is then proposed to explain the appearance of anomalous (induced) peaks in liquid chromatography. The conceptual model is applied to explain the production of induced peaks in reversed-phase ioninteraction chromatography. A quantitative, four-parameter thermodynamic model that assumes Langmuir adsorption of an added, charged surfactant (ion-interaction reagent) at the stationary phase-mobile phase interface is developed to describe retention of charged and neutral solutes in reversed-phase "ion-pair" liquid chromatography. The general interaction model and the thermodynamic model are then applied to a normal phase system.