28.1: Scope of HPLC

Gas chromatography consists largely of two specific types of interactions, both of which involve the stationary phase: the partitioning of the solute into a polar or a non-polar stationary phase, or the adsorption of the solute onto a solid packing material. The separation of a complex mixture into its component parts is determined primarily by the boiling points of the solutes and differences in the solubility of the solutes in the stationary phase. The properties of the mobile phase, on the other hand, are less important. It is not surprising that there is not much variety in the basic types of gas chromatography.

High-performance liquid chromatography consists of much richer group of techniques, both because the separation depends on the ability of the solutes to partition into the stationary phase and to partition into the mobile phase. The range of the possible types of interactions between the solutes and the stationary phase also is greater in HPLC than in GC. In addition to separations based on differences in solubility of the solutes in the stationary phase and the mobile phase (normal and reverse phase partition chromatography) and separations based on the adsorption of solutes on a solid substrate (adsorption chromatography), the separation of ions is possible using ion-exchange resins as stationary phases (ion-exchange chromatography) and the separation of ions by size (size-exclusion chromatography).

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