Guide
Bacteriostatic water, and why it is the default solvent.
Bacteriostatic water is sterile water with a preservative in it. That one difference is the reason a reconstituted vial can be entered more than once, and it is the reason people ask for it by name.
What is actually in it
Bacteriostatic water is water for injection with benzyl alcohol added, usually at 0.9 percent. The benzyl alcohol does not sterilise anything. It suppresses the growth of organisms that get in afterwards, which is a different job and the one that matters here.
Sterile water and normal saline are sterile at the moment they are sealed and have nothing to stop growth after that. This is why they are described as single-entry: once the stopper is pierced, the clock is short.
Why the preservative changes how a vial is used
A lyophilized vial usually holds more material than one aliquot. Without a preservative you would have to use the whole vial at once or accept that anything left is on a short timer. With bacteriostatic water the same vial can be drawn from repeatedly over a longer period.
This is also why the choice of solvent is not a detail. Reconstituting with sterile water and then treating the vial as multi-entry is the most common handling mistake we see people describe.
How to judge quality
The label should state the volume, that it is water for injection, and the preservative with its concentration. A bottle that names no preservative is not bacteriostatic water regardless of what the seller calls it.
The solution should be completely clear. Any haze, floaters or discolouration means the bottle is not usable, and that is true whether it cost a lot or nothing.
Check the seal and the expiry. A crimped cap that turns freely, or a flip-top that was already off, means the contents have been open to room air.
In Vietnam the common failure is not counterfeit water, it is water that has been decanted into an unlabelled bottle. If nobody can tell you what is in it, it is not a solvent, it is an unknown.
Handling in this climate
An unopened bottle is stable at room temperature and does not need refrigeration. Keep it out of direct sun, which in a Vietnamese apartment usually means keeping it in a cupboard rather than on a windowsill.
Once opened, the preservative is doing continuous work and the bottle has a finite life. Write the date you opened it on the label; it costs nothing and removes the guessing.
Wipe the stopper before each entry. In a humid climate that is not fussiness, it is the cheapest possible risk reduction.
Getting it here
We include bacteriostatic water free with orders of two or more peptides, and it is listed on its own if you only need the water. It ships alongside the rest of the order rather than separately.
If you want to work out what a given volume will give you as a concentration, the per-compound calculators do that arithmetic for the vial sizes we stock.
Common questions
Can I use sterile water instead of bacteriostatic water?
You can reconstitute with sterile water, but it contains no preservative, so the vial becomes single-entry. Bacteriostatic water is what makes repeated entry into the same vial workable.
Is bacteriostatic water the same as saline?
No. Saline is salt solution and has no preservative. Bacteriostatic water is water for injection with benzyl alcohol, usually 0.9 percent, which suppresses microbial growth after the vial is opened.
Does bacteriostatic water need to be refrigerated?
An unopened bottle is fine at room temperature, out of direct sunlight. Once opened, note the date and keep it clean and closed.
How much water should I add to a vial?
There is no single right answer. The volume you add sets the concentration, not the amount of material. Use the calculator for your compound to see what each volume produces.
Do you supply it?
Yes. It is free with any order of two or more peptides and is also listed on its own.