Importance of TFF for concentration

Filtration is a pressure-driven separation process that uses membranes to separate components in a liquid solution or suspension based on their size and charge differences. The two kinds of filtration, tangential flow filtration and normal flow filtration, are illustrated in figure below.

In Normal Flow Filtration (NFF), fluid is convected directly toward the membrane under an applied pressure. Particulates that are too large to pass through the pores of the membrane accumulate at the membrane surface or in the depth of the filtration media, while smaller molecules pass through to the downstream side. NFF can be used for sterile filtration, clarifying prefiltration, and virus/protein separations.

In Tangential Flow Filtration (TFF), the fluid flows tangentially along the surface of the membrane. An applied pressure serves to force a portion of the fluid through the membrane to the filtrate side. As in NFF, particulates and macromolecules that are too large to pass through the membrane pores are retained on the upstream side. However, in this case the retained components do not build up at the surface of the membrane. Instead, they are swept along by the tangential flow. This feature of TFF makes it ideal for finer sized-based separations, including ultrafiltration, and enables simultaneous concentration and buffer exchange.