Bacteriostatic water vs sterile water for reconstitution

Both are sterile. One contains a preservative. Which you use depends on how long the solution will be kept and what it will be used for.

Sterile water

Sterile water for reconstitution is purified water that has been sterilised and contains nothing else. It is the neutral choice: it introduces no additional compounds into the solution. Once a vial is opened it offers no protection against microbial growth, so a reconstituted solution in sterile water should be used promptly or divided into frozen aliquots.

Bacteriostatic water

Bacteriostatic water is sterile water containing 0.9% benzyl alcohol as a preservative. The benzyl alcohol inhibits bacterial growth, which allows a reconstituted solution to be drawn from repeatedly over a period without contamination becoming the limiting factor. It is the usual choice where a stock solution will be accessed more than once.

When the preservative matters

Benzyl alcohol is not inert. It can interfere with some cell-based assays and is incompatible with certain sensitive sequences. If a protocol specifies a solvent, follow it; if it does not and the downstream use is cell culture or an assay where the preservative might be a variable, sterile water with single-use aliquots is the safer default. When in doubt, reconstitute a small quantity in each and compare.

Handling either

Both should be treated as sterile products: use aseptic technique, do not reuse opened vials beyond their stated in-use period, and store as directed. Neither is intended for anything other than laboratory reconstitution of research materials.

For laboratory research use only — not for human or veterinary use. This article is general laboratory reference information and is not advice on the use of any product.