Amicon membrane integrity - (Aug/04/2007 )

Hi all,
I'd like to know how you check Amicon (Millipore) membrane integrity. I usually do it with Blue Dextran, and it works fine to membranes of 10 and 50 kDa. But it doesn't work for membranes up to 100 and 300 kDa. (I've tested four different membranes). They are all with "holes" ? Someone told me this method isn't suitable for the larger membranes, and I think that's really strange, since Blue Dextran has 2.000 kDa.
Thank you !!

probably this is due to two-fold : 1) blue dextran has a MW distribution of 2000 kDa, some may fall below that value. 2) dextran is a linear, rigid molecule and its cross-diameter is much smaller than its length. Some may pass through the filter due to either reason. Solution? Maybe you need to look into using a protein with higher MW (as they have narrower distribution) and not in linear shape.

Hi!
Thanks a lot !
Do you have an idea about another product that I could use?