INFLUENCE OF MOBILE PHASE-COMPOSITION ON EVALUATION OF LIPOPHILICITY BY PARTITION CHROMATOGRAPHY

The problems of the concentration dependence of retention indices and the applicability of extrapolated values in the evaluation of lipophilicity were studied. The reversed-phase high-performance liquid chromatography of arylalkanoic acids were carried out with experimental data for substituted estra-1,3,5 (10)-trienes, benzodiazepines, dermorphine derivatives and dansylamides selected from the literature for this purpose. Fair linear relationships between slopes of concentration dependences and extrapolated and non-extrapolated values of R(M) and log k' were found. Equivalence of these indices in the evaluation of lipophilicity can be inferred. Statistically significant dependences of log P (SIGMA-pi) values on concentration slopes make it possible to use them as new parameters of lipophilicity. The goodness of fit of these relationships increases when the values of E(T)(30), as a measure of the solvatochromic solvent polarity of mobile phases, are used instead of the change in modifier concentration.