USE OF MULTISTEP GRADIENT ELUTION TLC TO MODEL GRADIENT SEPARATION INHPLC

Silica gel, aluminum oxide, and cellulose plates have been tested for their capacity to separate the color pigments of red wine by both adso rption and reversed-phase TLC (RPTLC). As the color pigments of red ni nes could not be separated isocratically (some of the pigments remaine d at the origin if weaker mobile phases were used whereas others moved with the solvent front if eluent strength was increased) the applicat ion of multistep gradient development was investigated for separation of the pigments in one development using reversed-phase silica layers and water-methanol mixtures as mobile phases. RPTLC can be successfull y used for the separation of the color pigments of red nines, The pigm ent composition determined by RPTLC can facilitate identification of t he origin of the nine and aid discovery of adulteration with synthetic coloring substances. It has been further proved that multistep gradie nt elution in RPTLC can be used to predict the mobile-phase gradient w hich can, perhaps with slight modification, be used for the same separ ation in reversed-phase HPLC.