The determination of isotherm and prediction of retention values are the basis of the optimization of separation conditions of preparative chromatography.In this paper

the isotherms of ginsenoside Rg1 and Re from Panax ginseng were studied.Ginsenoside Rg1 and Re were prepared by chromatography column from Panax ginseng raw material

and the isotherms of ginsenoside Rg1 and Re were determined by frontal analysis (FA) on spherical C18 solid phase.The adsorption parameters G and b were set based on the competitive Langmuir model .In the mean time

the retention time of ginsenoside Re was obtained with the results of nonlinear chromatography theory.The calculated retention time were compared with that of experimental results with average relative error 3.68%.Additionally

some problems related to fitting based on the competitive Langmuir model were found and discussed.