DETERMINATION OF HYDROPHOBICITY PARAMETERS OF ANTIBIOTICS BY REVERSED-PHASE CHROMATOGRAPHY - THE EFFECT OF SUPPORT

The hydrophobicity and specific hydrophilic surface area of 29 antibio tics were determined by reversed-phase thin-layer chromatography using impregnated silica and alumina supports and methanol:water mixtures a s eluents. It was found that the supports retain their original retent ion characteristics even after impregnation influencing the reversed-p hase retention of antibiotics. It was established that the hydrophobic ity parameters are intercorrelated both on impregnated silica and alum ina layers, indicating that antibiotics behave as a homologous series of solutes, However, the correlations were not strong enough to substi tute the parameters with each other in quantitative structure-activity relationship studies, The specific hydrophobic surface areas determin ed on impregnated silica and alumina showed no significant correlation , proving the decisive role of support characteristics in the determin ation of this parameter.