ultrafiltration/diafiltration (UF/DF)

A tangential flow filtration step that concentrates the product (ultrafiltration) and exchanges its buffer for the formulation buffer (diafiltration), usually the last step of drug substance manufacturing. Membrane molecular weight cutoff, transmembrane pressure, flux and the number of diavolumes are the main parameters. As concentration rises, protein molecules interact more and aggregation risk increases, so UF/DF needs particular care for high-concentration antibody products. Japanese documents use UF/DF or TFF for the step.