Separation of dipeptides on a reverse-phase column: effect of non-linear intrinsic adsorption kinetics

Based on experimental results for the system of dipeptides (CBZ-leucyl-glycine and CBZ-glycyl-phenylalanine) on reverse-phase silica C₁₈, a detailed rate model including the intrinsic adsorption kinetics is proposed for multicomponent liquid chromatography. Simulation of the model was performed to investigate the effects of various parameters (rate constants, adsorption affinity, sorbent capacity, axial dispersion, feed concentration, sample size and velocity) on the band shape and spreading of elution chromatography. For cases with a finite rate of interaction between adsorbate and adsorbent, the mean retention time for the elution profiles of solutes is still determined by the equilibrium parameters, while the separation (resolution) between solute bands is largely influenced by the rate constants of the intrinsic adsorption kinetics. The effect of intrinsic adsorption kinetics becomes pre-eminent when the superficial velocity V_f is high. An optimal resolution diagram is presented to facilitate determination of the optimal operation parameters for touching-band separation.