The present invention is a method of separating recombinant human serum albumin (rHSA) from low molecular weight contaminants in a liquid, which method comprises the steps of: (a) providing a separation medium, which includes anion-exchanging ligands coupled to a base matrix; and (b) contacting the liquid with the separation medium to adsorb the rHSA to the ligands. In one embodiment, the functional groups of the ligands are weak anion-exchanging groups, preferably secondary amines, and the density of ligands on the base matrix is relatively high.