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

The compilation of the results obtained during the last 10 years on th e retention behaviour of homologous series in reversed-phase liquid ch romatography makes it possible to build a coherent model of molecular interactions for this type of sample. This model takes into account th e 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 aqueou s and non-aqueous reversed-phase liquid chromatography. The use of hom ologous series to investigate retention mechanisms gives the opportuni ty to distinguish between the solvophobic and the partition theories. Depending on the experimental conditions, both theories can explain th e results observed and the changes in retention pattern when altering one of the chromatographic parameters previously mentioned. The descri ption of the structure of the stationary phase as a brush, a picket fe nce or a stack is also integrated in the model. The experimental resul ts 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, polycyc lic aromatic hydrocarbons or carotenes.