Comparing the optimum performance of the different modes of preparative liquid chromatography.

A comparative study of the optimization of the different modes of the preparative separation of binary mixtures by liquid chromatography is presented. Band profiles were calculated by means of the equilibrium-dispersive model of chromatography in the cases of isocratic elution, gradient elution, and displacement chromatography. The objective function to be maximized was the product of the production rate and the recovery yield. The production rate was calculated using the same definition of the cycle time in all cases. This common definition accounts for column regeneration after each run in each mode of the separation. The calculations reveal that the number of experimental parameters to be adjusted to achieve optimum separations is relatively small. The major parameters are the loading factor and the number of theoretical plates, besides the displacer concentration in displacement chromatography, or the gradient steepness in gradient elution. The relative advantages of the different modes of preparative chromatography are discussed.