Bacteriostatic Water

Bacteriostatic water is sterile water containing 0.9% benzyl alcohol as a bacteriostatic agent. It is a laboratory diluent rather than a research compound.

The difference between bacteriostatic and sterile water is that benzyl alcohol. Sterile water is free of organisms at the point of manufacture and offers nothing against contamination introduced afterwards. The benzyl alcohol inhibits bacterial growth, which is what makes a vial multi-use across repeated withdrawals rather than single-use.

Supplied in a sealed multi-use vial with a self-sealing stopper.

Used to bring lyophilised compounds into solution. Introduced slowly against the vial wall rather than directly onto the powder cake, and the vial swirled rather than shaken, because peptide bonds are susceptible to shear and foaming complicates accurate withdrawal.

Volume determines concentration: a fixed mass of powder dissolved in a smaller volume yields a more concentrated solution, and the relationship is linear. Which volume is appropriate is a question for the laboratory rather than the supplier.

Stable at controlled ambient temperature while sealed. Once the stopper has been entered the bacteriostatic agent limits but does not eliminate the risk of contamination, and conventional laboratory practice is to treat an opened vial as having a defined working life rather than an indefinite one.

Stored away from direct light, and not frozen: freezing offers nothing here and risks the vial.