Step elution in preparative liquid chromatography

Preparative liquid chromatography with the step elution, in which a sample is loaded into a column at higher binding strength and then eluted at lower binding strength, was numerically simulated with a detailed rate equation model. The model takes into account film mass transfer resistance, pore diffusion, axial dispersion and local equilibrium. The step elution mode was compared with the isocratic elution mode in terms of the preparative performance for a binary mixture having a constant or variable separation factor. The effects of various parameters, such as step height, sample size, solute concentration, feed composition and mobile phase flow-rate, were examined.