Attila FelingerHungary

It is known in chromatography that the separation process and the migration rate of sample components through a porous stationary phase are highly influenced by the adsorption of each component. For the system which contains more than one component at a sufficient concentration (multicomponent system), their adsorption on the stationary phase will be influenced by each other, so it is important to characterize their competitive behavior. In SFC, competition is expected to occur between the organic modifier and the additive molecules when a ternary mobile phase (CO₂ + modifier + additive) is used for the separation of polar solutes. We elucidating the adsorption process of the mixture of modifier and additive on polar stationary phases in SFC, because there is still lack of information in describing the adsorption behavior of their mixture. There have not been many applications for the use of water as additive in the modified mobile phase in SFC comparing to bases or acids, because in most of the cases the use of additives usually is required for the separation of analytes with basic or acidic forms. Even though there are some applications by adding water to the mobile phase in SFC, but the role of water in the elution process still needs a dedicated study. Our objective is to show how water or methanol adsorption can influence retention and efficiency in SFC. For that purpose, a number of approaches of isotherm adsorption determination will be studied: the single component adsorption isotherm of either methanol and water, and the competitive adsorption isotherm of the water–methanol mixture.