Determination of adsorption isotherms in supercritical fluid chromatography

• The ECP, RTM, IM and PP methods were used to determine adsorption isotherms in SFC.
• Most modern SFC-systems are advantageous for determination of adsorption isotherms.
• Careful system verification with external sensors for mass flow etc. is necessary.
• The ECP, IM and RTM methods accurately predicted overloaded elution profiles.
• The more tedious PP method, could not accurately predict overloaded profiles.

In this study we will demonstrate the potential of modern integrated commercial analytical SFC-systems for rapid and reliable acquisition of thermodynamic data. This will be done by transferring the following adsorption isotherm determination methods from liquid chromatography (LC) to supercritical fluid chromatography (SFC): Elution by Characteristic Points (ECP), the Retention Time Method (RTM), the Inverse Method (IM) and the Perturbation Peak (PP) method. In order to transfer these methods to SFC in a reliable, reproducible way we will demonstrate that careful system verification using external sensors of mass flow, temperature and pressure are needed first. The adsorption isotherm data generated by the different methods were analyzed and compared and the adsorption isotherms ability to predict new experimental elution profiles was verified by comparing experiments with simulations. It was found that adsorption isotherm data determined based on elution profiles, i.e., ECP, IM and RTM, were able to accurately predict overloaded experimental elution profiles while the more tedious and time-consuming PP method, based on small injections on concentration plateaus, failed in doing so.