In this paper the metal affinity interaction chromatography (MAIC) model is employed in concert with appropriate mass transport equations to study preparative linear gradient chromatography in immobilized metal affinity chromatography (IMAC) systems. The MAIC model accounts for the nonlinear adsorption of proteins and mobile phase modulators (e.g., imidazole), and is shown to accurately predict gradient separations of proteins under overloaded conditions. Experimental and simulation results＇ indicate that the concentration-dependent sorption of imidazole and protein-imidazole interference effects can severely deform linear gradients in IMAC systems. The steric accessibility and displacer characteristics of imidazole together with multicomponent interference effects can lead to unusual protein elution profiles and the spiking of imidazole between the feed components. Due to their ability to act as displacers, these imidazole spikes can sharpen protein tails, decreasing the interface shock layer thickness and improving resolution. Finally, iterative optimization schemes are employed to study the influence of the transient displacer characteristics of imidazole shocks on the optimum operating conditions.