Preparative liquid chromatography : a study of the elution and displacement modes

Binary separations have been investigated experimentally and theoretically in overloaded elution, frontal and displacement modes of chromatography using phenyl-ethanol and phenyl-propanol as model compounds. The Rouchon-Golshan-Shirazi implementation of the semi-ideal model of chromatography was used to predict the individual component band profiles in these three modes. A competitive Langmuir isotherm with parameters determined from single component data gives fair prediction of the experimental data. The displacement effect is confirmed with accuracy and the tag-almg effect is demonstrated for the first time. Ifciwever, improved predictions can be obtained by measuring the binary isotherm directly by the method of hodograph transform. The effect of the sample size on the production rate for a binary mixture in overloaded elution chromatography was studied. The optimum sample size for component one is much larger than for component 2. The chromatogram obtained at the optimum sample size which maximizes the production rate for component two at constant column length, particle size and flow rate is such that the band of component one interferes just enough with that of component two to reach the purity requirements (i.e. 99 % yield).