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Filtering proteins and which membrane to use

Reference Number: AA-00350 Created: 04/06/2012 05:17 PM Last Updated: 04/06/2012 05:28 PM

Filters should not remove proteins or any other dissolved compounds from a solution. Filters have one purpose and that is to remove un-dissolved particles no matter what they are.


Some filters, depending on the membrane type and specifications, will adsorb compounds such as proteins to the membrane but if the solutions is analyte abundant, this will overwhelm the adsorptive capabilities of the membrane and the unwanted compounds will come through with the filtrate. This is called bringing the fitler to a steady state and may not be recommended for quantitative study.


If you want to remove a dissolved compound from a solution you should use SPE, centrifugation or a separation technique like flash chromatography. There are membranes available that are impregnated with chromatographic materials. These membranes will appear to be performing like a filter but are actually adsorbing and desorbing. One such material is the 3M brand called Empore.


At this time, we really do not offer any filters that are classified as low adsorbing for proteins however, PTFE and Nylon both adsorb some and not other proteins and are probably the best filters to use if you can. Unfortunately for most laboratories, it will be a hit or miss until you find the right brand of filter/membrane for your compounds keeping in mind, not all nylon are the same as some have surface charge and otheres, like ours does not. So it is safe to say that all filters are not created equally. Lastly do not think that once you tried one nylon filter, all nylon filters will perform the same way. That might prevent you from finding a brand/membrane that works well.


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