Headspace in 3ml injection pen vial?

[Romulusguy]

Question for those with experience: when transferring peptides into a 3ml pen vial, I often end up with some headspace. For instance, a 2 or 2.5ml transfer leaves roughly 0.5ml of air in the vial. I understand this is standard for pharmacy-issued vials, but I assume pharmacies operate in controlled, sterile environments; something my kitchen table definitely isn't. Should I purge the headspace before refrigerating (insert the vial into a pen, attach a needle, and advance the plunger until a drop appears, displacing the air), or is it safe to leave it as-is until I'm ready to use?

 

[joseblo]

Question for those with experience: when transferring peptides into a 3ml pen vial, I often end up with some headspace. For instance, a 2 or 2.5ml transfer leaves roughly 0.5ml of air in the vial. I understand this is standard for pharmacy-issued vials, but I assume pharmacies operate in controlled, sterile environments; something my kitchen table definitely isn't. Should I purge the headspace before refrigerating (insert the vial into a pen, attach a needle, and advance the plunger until a drop appears, displacing the air), or is it safe to leave it as-is until I'm ready to use?

Yes, you should purge the cartridge (vials don't have a plunger). Some videos show this. There are some 3D printed cart holders that have a little cylinder you can press them down on with the vent needle pushed in (if you're not using a vent needle you risk blowing the plunger out the back. I purge immediately after I filter so there's no extra needle, but you still need to install it in the pen with a needle on it and advance it until you get the last air (and a little squirt) out. 💦