Retention in capillary supercritical fluid chromatography

Abstract

Abstract Supercritical fluid chromatography (SFC) sometimes exhibits GC‐like behavior and sometimes LC‐like behavior, depending on conditions. However, it is not always clear whether one of these types of behavior, or a combination, operates for a particular set of conditions for every solute in a mixture. For example, some components may be partitioned mostly by their vapor pressures, while others, in the same mixture, are partitioned predominantly by solvent‐like properties of the mobile phase. Plots of retetion (as log of the capacity factor) vs . reciprocal temperature at constant pressure reveal a clear change in the character of the separation of well‐behaved solutes. A thermodynamic explanation of the observed behavior is given, based on the assumption that partitioning is controlled by the heats of solution of solute in the mobile and stationary phases. A model of SFC retention as it deviates from pure‐GC behavior on the same column is presented.