Air gap in a 3ml pen cartridge after peptide transfer?

[Romulusguy]

For people who've done this before: after I move peptides into a 3ml pen vial, there's usually a bit of empty space left. For example, if I transfer 2 or 2.5ml, about 0.5ml of air remains inside. I get that this is normal for vials that come from a pharmacy, but my assumption is that pharmacies work in controlled, sterile conditions — and my kitchen table is definitely not that. Before I put it in the fridge, should I clear out that air (put the vial in a pen, screw on a needle, push the plunger until a drop shows up, which forces the air out), or can I just leave it alone until I'm ready to use it?

 

[joseblo]

Romulusguy said:

For people who've done this before: after I move peptides into a 3ml pen vial, there's usually a bit of empty space left. For example, if I transfer 2 or 2.5ml, about 0.5ml of air remains inside. I get that this is normal for vials that come from a pharmacy, but my assumption is that pharmacies work in controlled, sterile conditions — and my kitchen table is definitely not that. Before I put it in the fridge, should I clear out that air (put the vial in a pen, screw on a needle, push the plunger until a drop shows up, which forces the air out), or can I just leave it alone until I'm ready to use it?

Yeah, the cartridge needs to be purged (a vial lacks a plunger). You can find demonstrations of this in certain videos. A few 3D printed cartridge holders feature a small cylinder; you push the cartridge down onto it while the vent needle is inserted (without a vent needle, the plunger might shoot out the back). I do the purge right after filtering, so no additional needle is needed, but you still have to put it into the pen with a needle attached and push until the remaining air (plus a tiny squirt) comes out.