RETENTION IN REVERSED-PHASE LIQUID-CHROMATOGRAPHY AS A FUNCTION OF MOBILE-PHASE COMPOSITION

The dependence of solute retention (k') on mobile phase composition (% B for binary-solvent mixtures A-B) is reviewed and compared with vario us empirical and theoretical equations that have been proposed for thi s relationship. Because the functional dependence of k' on organic mod ifier composition varies from one system to another, it is not possibl e from these data to draw any overall conclusions as to the nature of the retention process in reversed-phase chromatography. Likewise, ther e is probably no one best equation for extrapolating all retention dat a to O%B for purposes of predicting log P-o/w values from chromatograp hic data. The relative change in k' with change in %B can be described in terms of the parameter S = -d(log k')/d phi (pi = 0.01 %B). Values of S as a function of solute structure, mobile-phase composition, col umn type and experimental conditions are of interest for several reaso ns: insight into the retention process or ''mechanism'', mobile phase optimization, etc. Previous work relating to this question is reviewed here and some conclusions are presented.