The figure below shows a simple separation by chromatography. A continuous flow of solvent carries a solution of solutes A and B down a column. (a) As the solvent carries the two solutes down the column, we begin to see some separation of the solution. (b) At some later point in time, it can be seen that solute B is moving at a much faster rate than A. (c) In (d), solute B emerges first, while solute A finally emerges in (e). Thus, solute A has a greater affinity for the stationary phase than solute B. By varying the pH of the solvent or temperature of the column, the output of the column can be significantly altered, such as the timing of when individual species emerge.