Molecular imprinting is a most attractive method of preparation of dedicated stationary phases for chromatography. Its use for enantioseparations is attracting considerable interest. 1,2 Imprinted materials can provide a very high selectivity for the objective compound, i.e., the imprinted molecule. [1][2][3][4][5] Although analytical applications are rapidly developing, the situation on the preparative front is less rosy. 1 Columns packed with imprinted stationary phases exhibit a poor efficiency and elution peaks are often unsymmetrical, especially for the more retained enantiomer. Sellergren et al. 1,2 suggested that the nonlinear behavior of the adsorption isotherm was the main cause of the broad and unsymmetrical bands observed for L-phenylalanine anilide (PA) on an L-PA imprinted chiral stationary phase. Although the possibility of a slow mass transfer kinetics was also pointed out, no detailed study supported this assumption. Yet, information on the mass transfer characteristics of imprinted stationary phases is necessary to clarify strategies for the improvement of these materials.Most kinetic studies in chromatography assume that four mass transfer processes are involved in a column, (1) axial dispersion, (2) fluid-to-particle mass transfer, (3) intraparticle diffusion, and (4) adsorption/desorption. 6 The contributions of these four processes to peak spreading are evaluated separately. Axial dispersion and the fluid-to-particle mass transfer resistance are inherent to flow processes through packed beds. They are well understood, relatively easy to control, and their contributions are often small. By contrast, intraparticle diffusion and adsorption/desorption give often larger contributions to the mass transfer resistance in the column. Their properties are intrinsic to each packing material and they are still often poorly understood. In order to evaluate the actual performance of packing materials, the characteristics of the mass transfer kinetics inside stationary phase particles must be clarified.Sajonz et al. 7 measured the adsorption equilibrium isotherm and the mass transfer kinetics of L-and D-PA on a polymeric stationary phase imprinted with L-PA, using a staircase frontal analysis method. The isotherm was well represented by either the Bi-Langmuir or the Freundlich models, but not by the simple Langmuir isotherm. The equilibrium data suggested that the distribution of the adsorption energy on the surface of the imprinted stationary phase is heterogeneous and showed that this phase has a high selectivity for the imprinted L-enantiomer. The lumped mass transfer rate coefficient (km,L) was calculated from each single breakthrough curve by applying the transport model of chromatography. 6 The values of km,L increased with increasing concentration of the enantiomers. The extent of the positive concentration dependence of km,L was larger for L-PA than for D-PA. It is expected that a more detailed analysis of the overall mass transfer rate parameter, km,L, could provide new, useful information and all...