Sterility guidelines that I've come across and put to work when needed....
You always read that when transferring an oil based substance such as an AAS that you should do all the sterile procedures...
1. Make sure the sealed vial you are using is indeed sterile and trust whom you buy off of.
2. It's best to use a whatman or some kind of filter when transferring, you can never be too safe.
3. Always swab the tops of the vials directly before you stick the pin in that you're using to transfer the gear, etc, into the new vial. The same goes for the pin that you use to draw the substance with.
4. Try to leave the same needle that's used in the new sterile vial in the rubber stopper. This way you won't be having 10 million holes in your new vial's stopper, and also the less you poke into the new vial, the less you have to worry about sterility issues.
5. Make sure to heat the oil up in the old vial as it will be a lot easier to transfer this way.
*Most people like to use a single, large or rather larger vial to put the newly filtered gear into. This can definately be useful and no doubt more convenient, but when it comes down to sterility issues it's best to use several smaller vials, IE: say instead of one 50ml vial, use five 10ml vials.
During the injection procedure, one will first fill the syringe up with air and then unload it into the vial in order to make it easier when drawing. However when doing this, not only are you drawing up air but the bacteria, etc. that comes along with it. Then you go and shoot that into your vial, and voila, you got yourself a vial with sterility issues. So, when your using a larger vial say 50ml, the chances of getting an abcess are amplified due to the amount of drawings you do from it.
With using a smaller 10ml vial, the issues will be lowered and the possibility of an abcess is greatly lessened.
Baking is also an option but can sometimes do more harm than good. Make sure to read up on what temperatures your said substance can withstand so you do not ruin your past efforts.