There has been an extensive development in the area of preparative Supercritical Fluid Chromatography (SFC) the last years and many pharmaceutical companies has replaced their preparative Liquid Chromatography (LC) systems with SFC one with higher production rates and that are less harmful to the environment. However, there are still many unresolved fundamental issues, e.g. the advanced theory necessary to correctly model and scale-up SFC is still missing. The compressibility of the mobile phases in SFC generates density, temperature and pressure variations and makes it more complicated to model than LC.

Today there only exist a handful studies that deals with the determination of adsorption isotherms in preparative SFC, and only rarely are the results verified by comparing simulated and experimental overloaded elution profiles. Proper characterization of the adsorption processes is necessary for deeper understanding of analytical and preparative applications and therefore this is a very important area to study.

In this lecture we will demonstrate the potential of modern integrated commercial analytical SFC-systems for rapid and reliable acquisition of thermodynamic data by transferring several adsorption isotherm determination methods from LC to SFC. The adsorption isotherms determined by the different methods were analyzed and compared and their ability to predict new experimental elution profiles was verified by comparing experiments with simulations. Based on these results we will discuss the major differences with LC and the methods advantages and drawbacks when used in SFC. In addition, guidelines will be given for how to avoid the most important pitfalls, e.g., we found that careful system verification, using external sensors of mass flow, temperature and pressure, is necessary for reliable determinations of adsorption isotherms.