A previously developed Flory-type mean-field analysis of the mixing of a multicomponent, polydisperse solvent with an interphase of terminally anchored chains of finite extensibility is utilized in the determination of the chromatographic properties of the interphase. In the limit of dilute solute species this approach leads to simple, analytical expressions which describe the partitioning and retention of solute molecules in the interphase. These interphases could be surface-grafted polymer layers or block polymers at interfaces. The partitioning and retention of solute molecules in the interphase depend on the chain configurations, the entropy of mixing, and the contact interaction among the species present. The theory allows for the calculation of average or global properties such as the polymer, solvent, and solute volume fractions in the interphase, the interphase thickness, and solute partition coefficients and retention factors. The partitioning and retention of the solute molecules are found to depend explicitly on the surface density of the terminally anchored chains, solvent strength, terminally anchored chain length, solute size, and the various interactions among the species present. Size exclusion and enhancement, affinity, and gradient chromatography are considered.