GENERAL VIEW OF MOLECULAR INTERACTION MECHANISMS IN REVERSED-PHASE LIQUID-CHROMATOGRAPHY

The compilation of the results obtained during the last 10 years on the retention behaviour of homologous series in reversed-phase liquid chromatography makes it possible to build a coherent model of molecular interactions for this type of sample. This model takes into account the effects of the chain length and the polarity of the sample molecule. It rationalizes the influence of the bonding density and the function nature (monomeric/polymeric) of the stationary phase and the role of temperature and the nature of the organic modifier in partially aqueous and non-aqueous reversed-phase liquid chromatography. The use of homologous series to investigate retention mechanisms gives the opportunity to distinguish between the solvophobic and the partition theories. Depending on the experimental conditions, both theories can explain the results observed and the changes in retention pattern when altering one of the chromatographic parameters previously mentioned. The description of the structure of the stationary phase as a brush, a picket fence or a stack is also integrated in the model. The experimental results accumulated with homologous series also suggest that the molecular interaction mechanisms governed by molecular recognition sites differ for molecules that are members of different homologous series, polycyclic aromatic hydrocarbons or carotenes.