5.1   How do I choose a membrane for my filtration application?

It is important to understand the potential affects a membrane can have on filtered solutions. We offer Cellulose Nitrate, Cellulose Acetate, Nylon, and Polyethersulfone membranes, each with specific characteristics in wetting agents, protein binding, DNA binding, and chemical resistance.

• PES is best for filtering cell culture media and other biological solutions. It has high flow rates, lower protein binding and extractables. For additional information please refer to the Corning Filter Selection and Use Guide.



• Cellulose Acetate also has low binding affinities for most macromolecules and is recommended for low protein binding applications such as cell culture media containing serum.



• Nylon is recommended for applications requiring low extractables. The membrane is naturally hydrophilic and has a greater chemical resistance.



• Cellulose Nitrate is recommended for filtering solutions that do not contain proteins.

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5.2   How do I mix and match bottle top filters with the appropriate bottles?

The bottle top filter should match the neck size of the bottle. Corning bottle top filters have either a 33mm or 45mm neck size and must be matched with the same neck size bottles. Note: The plastic Corning storage bottles and the glass Pyrex media bottles have a 45mm neck.

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5.3   Which filter membrane is recommended for filtering tissue culture media?

PES is recommended due to its low protein binding and low extractables in addition to its faster flow rate. Cellulose acetate is also good. For additional information please refer to the Corning Filter Selection and Use Guide.

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5.4   Which filter membrane is recommended to use with organic chemicals?

Corning Nylon filter membranes have moderate to higher resistance to most organic chemicals. Teflon (PTFE) filter membranes have the best chemical resistance but are not available in vacuum filters. For specific applications, call technical service or do a test filtration run. Remember the chemical compatibility of the filter housing must also be considered. For additional information please refer to the Corning Filter Selection and Use Guide.

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5.5   What membrane type is best suited for filtering protein solutions?

Cellulose acetate or Polyether sulfone will both work well, the only difference being that cellulose acetate has wetting agents added to it.

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5.6   Can mycoplasma go through a 0.2 micron filter?

A 0.2 micron filter does not prevent the passage of all mycoplasma if the solution is heavily contaminated; although, it will reduce their concentration by several orders of magnitude.

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5.7   When is it recommended to use a 0.45 micron pore size filter instead of a 0.22 micron pore size filters?

A 0.45 micron filter is recommended for clarification of a solution since filtering with it may not produce a sterile product. Filtration through a 0.22 micron filter is far more likely to produce a sterile product (except for possibility of mycoplasma and viruses).

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5.8   When should I use a prefilter during filtration?

A prefilter improves the efficiency of filtration and enhances the life of the actual membrane, especially in the presence of visible particulates. The use of a prefilter is highly recommended as the easiest and most economical way of improving filter performance. For information about Corning’s fiberglass prefilters, including recommended sizes to order for the apparatus being used, click here.

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5.9   What is the recommended maximum force for the Spin-X Centrifuge Tube Filter?

The maximum force for the Spin-X is 16,000 xg. Relative centrifugal force can be determined with a nomogram using the radius from the centrifuge spindle to the particular point along the tube and the RPM of the centrifuge.

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5.10   Which FiltrEX filter plates should I use for my application?

Corning provides 96-well and 384-well filter plates with PVDF and with glass fiber filters. The low-binding hydrophilic PVDF membrane can be used for lysate clarification, protein kinase assays, or bead- or resin-based separation assays. The glass fiber filter plates can be used for a variety of applications, such as plasmid isolation, DNA purification, PCR clean-up or receptor/ligand binding assays. Click here to visit our Technical Information Center for additional application information.

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