LIPOPHILICITY DETERMINATION OF NONHOMOLOGOUS SERIES OF NONIONIC SURFACTANTS BY MEANS OF REVERSED-PHASE THIN-LAYER CHROMATOGRAPHY

The lipoPhilicity and specific hydrophobic surface area of 22 nonionic surfactants having different hydrophobic moieties have been determine d by reversed-phase thin-layer chromatography using methanol as an org anic modifier. R(M) values decreased linearly with increasing concentr ation of methanol. Both the lipophilicity and specific hydrophobic sur face area of the surfactants decreased with increasing numbers of ethy lene oxide groups per molecule. The significant correlation between th e R(M0) value and the specific hydrophobic surface area indicates that these surfactants can be considered as a homologous series of solutes independently of their structural inhomogeneity. Stepwise regression analysis suggested that the hydrophobic moieties are not entirely solv ated and they are in a folded state in the eluents.