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Bacteriostatic water vs sterile water

The difference between bacteriostatic water and sterile water for reconstituting lyophilised research peptides, and when labs use each.

Sterile water

Sterile water is water that has been sterilised and contains nothing else. With no preservative, once a vial is opened it can be contaminated, so it is generally treated as single use.

Bacteriostatic water

Bacteriostatic water is sterile water with 0.9% benzyl alcohol added. The benzyl alcohol doesn't sterilise anything, but it stops bacteria from multiplying, which is why a vial can be accessed more than once.

Which do labs use?

Bacteriostatic water is common for reconstituting lyophilised peptides when a vial will be accessed several times. Sterile water is used when a preservative must be avoided, for example where benzyl alcohol could interfere with an assay or with the stability of a particular compound.

Check the requirements of the method you are following. Store unopened bacteriostatic water below 25 °C and, once opened, at 2–8 °C.

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