Feed throughput in preparative, steady-state two-dimensional chromatographic separations can be improved by injecting feed along a line that is slanted into the two-dimensional apparatus while solvent is continuously fed to the bottom of the apparatus. The local equilibrium model of adsorption is applied to the rotating annulus geometry to show that throughput can be increased without decreasing resolution. The model is then related to the solute trajectories, and the results for two-dimensional paper and gel permeation chromatography are derived. Two-dimensional countercurrent distribution is also considered and an exact solution is developed. The slanted feed line technique decreases thermodynamically irreversible mixing and thus is more efficient.