SHAPE SELECTIVITY IN REVERSED-PHASE LIQUID-CHROMATOGRAPHY FOR THE SEPARATION OF PLANAR AND NONPLANAR SOLUTES

Solute retention in reversed-phase liquid chromatography is the result of a variety of complex interactions between solute, mobile phase and stationary phase species. An understanding of the parameters that influence retention is useful in the development of separation methods with existing columns. Such knowledge is even more important for the design of new bonded stationary phases with engineered chromatographic properties. This review will examine some of the factors that affect retention and selectivity with alkyl-modified sorbents, particularly for the separation of solutes with well defined, rigid structure (e.g., polycyclic aromatic hydrocarbons). The chromatographic discrimination of compounds on the basis of molecular structure, namely ''shape selectivity'', will be studied in terms of contributions from bonded phase morphology, and in terms of operational conditions. An emphasis is placed on practical choices that are available to control selectivity and optimize separations for isomers and related mixtures.