Q: What is tangential flow filtration (TFF)?
Tangential flow filtration (TFF) is a method in which the feed flows along the membrane surface, generating tangential shear to reduce membrane fouling and clogging. TFF is commonly applied as ultrafiltration (1–1000 kDa) or microfiltration (0.1–0.65 µm).
Q: How to choose the appropriate ultrafiltration membranes?
For most ultrafiltration and dialysis applications, both PES and RC membranes are suitable choices.
PES membranes can meet a wide range of application needs for most protein and small-molecule products, such as antibodies, APIs, and vaccines.
RC membranes should be considered when preparing high-concentration formulations, applications containing organic solvents (e.g., ADC products), or concentration/exchange of linear molecules including oligonucleotides and peptides.
For new target molecules, it is recommended to test both membrane types during standard sample handling and process optimization.
Q: How to select the appropriate cut-off for ultrafiltration cassettes?
Choose the membrane cut-off based on the size or molecular weight of the substance to be separated or retained:
Antibody proteins: 30 kDa or 50 kDa
Viral or vaccine products: 100–1000 kDa
For API products, an appropriate molecular weight cut-off (MWCO) can be selected from the range of 1 kDa, 2 kDa, 3 kDa, 5 kDa, 8 kDa, and 10 kDa according to the process objectives.
If the molecular weight of the target substance is unknown, preliminary testing can be performed using ultrafiltration centrifugal devices with different cut-offs to identify the most suitable molecular weight retention.
Q: What materials and cut-offs are available for Cobetter cassettes?
Ultrafiltration cassettes are available in PES and RC membranes, with cut-offs ranging from 1–1000 kDa.
Microfiltration cassettes are available in PES and PVDF membranes, with pore sizes ranging from 0.1–0.65 µm.
Q: Can ultrafiltration cassettes be reused?
Yes. Ultrafiltration cassettes can be reused by selecting appropriate cleaning methods. However, due to changes such as declining membrane flux and increased permeation, the cassettes should be replaced periodically as needed.
Q: How should ultrafiltration cassettes be cleaned?
They can be cleaned by circulating 0.1-0.5 M sodium hydroxide (NaOH) solution. If cleaning effectiveness is insufficient, adjustments can be made by either of the following methods:
Increasing the cleaning solution temperature (<45 °C)
Adding sodium hypochlorite (NaClO, 500 ppm)
Extending the cleaning time
For difficult-to-clean feed components, alternative cleaning solutions such as acidic solutions, alcohols, or surfactants may also be used.
Q: Are Cobetter ultrafiltration membrane cassettes compatible with hardware from other companies?
Yes. They can be installed in holders from Merck, Pall, and similar manufacturers. But it is necessary to ensure proper torque and perform integrity testing.
For Sartorius holders, a specific adapter plate is required for proper installation.