A method of purifying a bispecific antibody consisting of two copies of a single heavy chain polypeptide and a first light chain comprising a kappa constant region and a second light chain comprising a lambda constant region, the method comprising the steps of: (a) providing a mixed antibody composition that comprises one or more of the bispecific antibodies consisting of two copies of a single heavy chain polypeptide and a first light chain comprising a kappa constant region and a second light chain comprising a lambda constant region (bispecific Ab); one or more monospecific monoclonal antibodies having two lambda light chains or portions thereof (λ-MAb); and one or more monospecific monoclonal antibodies having two kappa light chains or portions thereof (κ-MAb); (b) providing a separation means that has a specific affinity for a kappa light chain constant region or a lambda light chain constant region, wherein the separation means is coupled to a ligand having high specificity and affinity for a kappa light chain constant region or a lambda light chain constant region, and wherein the ligand is an anti-lambda monoclonal antibody or an anti-kappa monoclonal antibody; (c) contacting the separation means with the mixed antibody composition under conditions that allow for differential binding to the separation means by the bispecific Ab as compared to the binding to the separation means by the kappa light chain constant regions of the κ-MAb or by the lambda light chain constant regions of the λ-MAb; and (d) eluting antibodies from the separation means under conditions that allow for preferential detachment of the bispecific Ab as compared to the detachment of the kappa light chain constant regions of the κ-MAb or the detachment of the lambda light chain constant regions of the λ-MAb; wherein the binding and/or elution conditions are selected from one of: a step variation in pH level, a step variation in the concentration of inorganic salt, a step variation in the concentration of an amino acid in the mixed antibody composition, or the inclusion of one or more denaturing agents. (a) providing a mixed antibody composition that comprises one or more of the bispecific antibodies consisting of two copies of a single heavy chain polypeptide and a first light chain comprising a kappa constant region and a second light chain comprising a lambda constant region (bispecific Ab); one or more monospecific monoclonal antibodies having two lambda light chains or portions thereof (λ-MAb); and one or more monospecific monoclonal antibodies having two kappa light chains or portions thereof (κ-MAb); (b) providing a separation means that has a specific affinity for a kappa light chain constant region or a lambda light chain constant region, wherein the separation means is coupled to a ligand having high specificity and affinity for a kappa light chain constant region or a lambda light chain constant region, and wherein the ligand is an anti-lambda monoclonal antibody or an anti-kappa monoclonal antibody; (c) contacting the separation means with the mixed antibody composition under conditions that allow for differential binding to the separation means by the bispecific Ab as compared to the binding to the separation means by the kappa light chain constant regions of the κ-MAb or by the lambda light chain constant regions of the λ-MAb; and (d) eluting antibodies from the separation means under conditions that allow for preferential detachment of the bispecific Ab as compared to the detachment of the kappa light chain constant regions of the κ-MAb or the detachment of the lambda light chain constant regions of the λ-MAb;