filter opinions

[MMI]

Not all .45 um filter are not all treated the same. I have tried to types, Whatman .45 um pvdf and Millipore .45 pvdf membrane and found that the whatman filters seem to be able Pre-filter more oil through before clotting. My question is Whatman filters as efficient as Millipore? For pre-filtering, what type of membrane for our pupose do we choose and why?

[Skyefire]

pvdf what we generally use, most chem resistant and whatman types (not all) include a prefilter in it. some of the cheaper whatmans don't have it and boy can you tell the differnce. Millpore is said to be good as well.