Methods of separating triple-light chain (H2L3) antibodies (e.g., anti-CD123 H2L3 antibodies) or antigen-binding fragments thereof from an antibody composition comprising H2L3 antibodies or antigen-binding fragments thereof and double-light chain (H2L2) antibodies (e.g., anti-CD123 H2L2) or antigen-binding fragments thereof are provided.