This is the first post in the series The Fundamentals of Tangential Flow Filtration.

Jim Simmons is the Senior Director of Education at SpectrumLabs.com. He has over 30 years experience in membrane separations and spent 15 years as the Regional Sales Manager for the central United States. Jim now conducts the Spectrum Lab’s Training and Education Program.

The series will:

  1. Define Tangential Flow Filtration (TFF)
  2. Address the two main TFF platforms and gain an understanding of how they differ
  3. Discuss methods to develop a bioseparations process using TFF to accomplish the three main TFF applications
  4. How to optimize the process
  5. How to scale up the process

Many methods are used to perform separations in the biotech world. These include:

  • Affinity separation – Chromatography
  • Centrifugation
  • Membrane separation – TFF
    • Flat membrane: Dialysis, Spiral, Plate & Frame, Cassettes
    • Hollow Fiber membrane, Modules

In TFF, the membrane forms a barrier through which only a portion of the soluble material is allowed to cross. This is accomplished by flowing the sample across the surface of the membrane (tangential flow) while applying pressure to cause a portion of the soluble species to cross the membrane. This technique avoids plugging (fouling) the membrane and allows for extended processing, thereby desirable for larger volume processes. The retained species remains in solution and is easily recovered after the process. Although the word filtration is in the name, TFF is not a filtration process in the classic sense of the word, which generally refers to single-pass filtration – where particles too large to pass through the filter are trapped. This results in the filter plugging with solids, and it is difficult to recover the retained material.

It is very likely you will have a need for a TFF process. Why? Because the commonly taught methods of separation do not meet these criteria:

  • The method of separation must be fast
    • As scale increases, so also does the need for faster processing.
  • The method of separation must be scaleable
    • As the need for scale up emerges, a process defined at the bench scale mimic the process at the larger scale
  • The method of separation must be repeatable
    • It is important to have a process that performs reliably the same from one run to another.
  • The method of separation must be validatable
    • The process must be robust and conform to regulatory standards.

Therefore as the scale of the process increases, so also does the probability that centrifugation or dialysis will become inadequate to the task.  At this juncture, a working understanding of TFF is indispensible.

Next:  A comparison of the two main TFF platforms– Hollow Fiber and Flat Membrane.