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Cross Flow Filtration (Tangential Flow Filtration)
Cross flow filtration can be used at several different stages in downstream purification. Several formats exist including hollow fibre and flat sheets.
A filtration technique in which liquid flows across the surface of a membrane while under pressure. The pressure drives the liquid through the membrane. CFF has a sweeping action across the surface of the membrane, which minimizes formation of a gel layer and subsequent fouling. The feed solution flows parallel to the surface of the membrane. Driven by pressure, some of the feed solution passes through the membrane filter. Most of the solution is circulated back to the feed tank. The movement of the feed solution across the membrane surface helps to remove the buildup of foulants on the surface. In conventional filters, the liquid flows perpendicular to the filter surface, and all the feed passes through the filter. Also called tangential flow filtration.
Microfiltration (MidGee, Xampler, MaxCell, ProCell)
- Pressure-driven membrane-based separations process in which particles and dissolved macromolecules larger than 0.1 µm are rejected (collected). The process of removing particulates primarily from liquids by passing the liquid sample through a microporous membrane. This term usually refers to the removal of particles between 0.1 microns to 5 or 10 microns in size. The first step in separations process development and optimization is to choose the appropriate membrane pore size. Choose MF cross flow cartridges for applications requiring small (0.1 to 5 µm) pores, high porosity, and low dirt holding capacity. For example, our customers use a considerable number of MF cross flow cartridges for retention of microorganisms and for analytical processes.
Diafiltration (MidGee, Xampler, MaxCell, ProCell)
- The fractionation process of washing smaller molecules through a membrane, leaving the larger molecule of interest in the retentate. It is a convenient and efficient technique for removing detergents, separating free from bound molecules, removing low molecular weight materials, or rapidly challenging the ionic or pH environment. Crossflow or tangential flow filtration in which the desired product of particles or small molecules pass through the membrane to be collected.The opposite of concentration.
Ultrafiltration (MidGee, Xampler, MaxCell, ProCell).
- Pressure-driven membrane-based separations process in which particles and dissolved macromolecules smaller than 0.1 µm and larger than approximately 2 nm are rejected. This filtration process separates suspended and/or dissolved materials based primarily upon their size.
The first step in separations process development and optimization is to choose the appropriate membrane pore size. Choose UF cross flow cartridges for applications requiring .001 to .05 µm pores (1,000 to 1,000,000 nominal weight cutoff). For example, choose ultrafiltration cartridges for retention of bacteria, viruses, proteins, and polymers.
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