Antibody fragments — such as fragment antigen-binding (Fab) domains, single-chain variable fragments (ScFvs), and heavy-chain variable domains (nanobodies) — have emerged as increasingly important therapeutic and diagnostic alternatives to full-length monoclonal antibodies (MAbs) for a multitude of diseases. Whereas MAb downstream processing is well established and easy to scale based on protein A capture, the purification of antibody fragments is just on the verge of standardized processing. The most promising candidate for effective capture of those containing a kappa light…