Any trouble blowing out the filter? I've heard filtering more than 1ml through a 4mm is likely to blow out the filter unless you go super slow.
I've heard/read the same.
I don't think it's the amount as much as the differential pressure being applied. You exert a certain force on the plunger as you filter. The larger the filter the more dispersed the force. Keep this in mind when using a 4mm filter, as it's easy to apply to much force and tear the filter membrane.
This is why I said be patient when using a 4mm filter. 4mm is designed for volumes <1ml. 13mm for 1-10ml.
13 mm is a waste of peptide for under 3 mL. I know there are different viewpoints, but I want the most peptide in the vial. A constant, steady pressure of a lb or two works fine.
For me it's more about the mg of peptides being filtered. It isn't the BAC that clogs the filter but the contaminates that you’re trying to remove.
I go by reconstitution volume. 30 mg of Semax looks the same as 10 mg. One gets 500 mcg of BAC and one gets 1 mL of BAC, and I use the same 4 mm filter either way.