Small-molecule impurities that bind to and copurify with protein biopharmaceuticals traditionally have been removed using bind-and-elute (BE) chromatography. However, that approach may be undesirable for a number of reasons. For instance, it may present a facility-fit challenge or provide a lower process yield than what is acceptable. A common scenario in which BE chromatography may be undesirable is in removal of unreacted conjugation reagents. Bioconjugates represent an important and growing class of pharmaceuticals that include PEGylated proteins, vaccines, and antibody–drug…