"Air Flushing" 13mm 0.22um PES filters?

[PatchyFog]

So, on another platform, which one I can't recall now, I saw the results of holdback (I think) tests done on various brands of 13mm PES filters and they did both BAC flushing and "air flushing" where they pushed what seemed to be a full syringe of air through the filter to flush it after finishing with the liquid.

Today, as I was recon-ing, I thought "Gee, that would be a good way to do it, then I don't have to think about holding reserve liquid for the flush." So, after the peps were in the vial/cart (was doing both), I unscrewed the syringe from the filter, drew in a full shot of air, and then screwed the syringe back onto the filter and tried to push the air through.

Well, it sort of worked. About 1/2 to 2/3 of the air in my 3 ml syringe went in easily and I saw about 5 or 6 drops of hold back come out of the filter and drip into the vial, but after that, it became impossible to push the plunger down further and I felt I was going to blow the PES membrane if I pushed any harder. Yes, the vial/cart was vented and yes, it was still impossible to push even if I removed the filter/syringe combo from the needle and tried to squirt the air into the air. Which leads me to think the filter material itself swells up or something when you try and force air into it and/or it goes dry and then becomes opaque. (Both Biologix brand and no-name generic.)

Anyway, just wondering if I "did it right" or if there is some special technique to an air flush I don't grasp. I realize this way of working is kind of niche; I hadn't heard of it until I read this study. Also, I am working in a laminar-flow area, so I'm not as concerned about injecting a bunch of bio-loaded room air into the vial as I would be if I were not.

Thanks for any insights.

 

[Aussiegreenmachine]

From what I've read, air purging works best on the 4mm filters and you can expect 1/3 to 2/3 of the remaining liquid in the filter to push through. This is from tests on STG, if I recall. The same testing also showed that even though some BAC may remain in the filter, the majority of peptide is pushed through into the cart/vial, so it's essentially a slightly higher concentration (ie: minus the 5 iu or so that remains behind). The upshot was that it was negligible. For myself, I have settled on air purging 4mm filters and BAC purging with 13mm filters. TBH I've only used 4mm filters so far and they've been just fine. If I need to filter GHK-cu or something like that I'll use a 13mm.

 

[Zelmar702]

When the plunger stops or "fights back" during air injection, it typically means the vial is already at its maximum pressure capacity. This indicates the vial has reached its limit and further air injection will not be possible. Just use less air.

 

[PatchyFog]

When the plunger stops or "fights back" during air injection, it typically means the vial is already at its maximum pressure capacity. This indicates the vial has reached its limit and further air injection will not be possible. Just use less air.

As I noted the vial was vented. And even after removing the needle (but not the filter) the plunger would not move. Both indicate the filter itself is creating the resistance.

 

[Chili777]

As I noted the vial was vented. And even after removing the needle (but not the filter) the plunger would not move. Both indicate the filter itself is creating the resistance.

There is a certain "dud" rate for all filters. Some manufacturers have higher rates than others. If it's clogged early, you either have a dud or it did it's thing. If you've pushed a couple mL through and got 5 or 6 drops of the hold back volume, I'd call it good with a 4 mm.