Fundamental Investigations of Adsorption in SFC

Sammanfattning: In supercritical fluid chromatography (SFC), the eluent is composed by carbon dioxide, often with additional components, in a condition between gas and liquid. This thesis aims to reach a deeper understanding of SFC by revealing the function of the additional eluent components through systematic adsorption studies.In Paper I, investigation of surface excess adsorption isotherms of methanol revealed that a monolayer of methanol was formed. In Paper II, severe peak deformation effects due to this adsorption were shown. The findings in these papers revealed that a competitive additive model best predicts the solute retention at low methanol fractions whereas at higher fractions, methanol acts just as a modifier. In Paper III, the generality of the effects was proven by investigation of several co-solvent and stationary phase combinations. In Paper IV it was investigated how the robustness of SFC separations depend on the co-solvent adsorption, pressure, and temperature. In Paper V, the impact of the addition of amine additives was investigated. Two different mechanisms for solute peak deformations were observed.The knowledge achieved about SFC in this theses provides guidelines for development of more robust SFC methods where peak deformations/distortions can be avoided.