Bacteriostatic water, sterile water and acetic acid 0.6%: laboratory diluents explained

Bacteriostatic water is sterile water that contains 0.9% benzyl alcohol (9mg per mL) as a preservative. The benzyl alcohol inhibits the growth of bacteria that might be introduced when a vial is accessed more than once. This guide explains how it differs from plain sterile water and from 0.6% acetic acid, and what to check on the label.

Laboratory diluents at a glance

What does “bacteriostatic” mean?

Bacteriostatic means inhibiting bacterial growth. It does not mean sterilising. Bacteriostatic water starts sterile, and the benzyl alcohol is there to slow the growth of any bacteria introduced later, which is why it is the usual choice when a vial will be accessed several times. Sterile water contains no preservative, so it offers no such protection once opened.

What are the identifiers?

Where does 0.6% acetic acid fit?

Solubility depends on the compound. Some lyophilised materials dissolve readily in water at near-neutral pH, while others, typically more basic peptides, dissolve more readily in a mildly acidic solvent. Dilute acetic acid is a standard laboratory solvent for that second group. The appropriate solvent for a given material is a matter for the documentation supplied with it and your laboratory’s own procedures.

What should the label and documentation show?

• The composition, including the benzyl alcohol or acetic acid concentration.
• The volume per vial.
• The batch number and expiry date.
• An intact seal and a clear, particle-free solution.

How should diluents be stored?

Keep vials sealed, out of direct light and within the temperature range on the label. Record the date a vial is first accessed, and follow the label and your institution’s procedures for how long an accessed vial may be kept. Do not use a solution that has become cloudy or discoloured.

How are diluents supplied by Ascend Research?

Bacteriostatic Water is listed in 3ml and 10ml vials and Acetic Acid 0.6% in a 3ml vial, both dispatched from within Australia. They are grouped under laboratory supplies. The [2V] Retatrutide + Bacteriostatic Water Set supplies the two items separately.

Frequently asked questions

What is bacteriostatic water?

Bacteriostatic water is sterile water containing 0.9% benzyl alcohol, a preservative that inhibits the growth of bacteria in a vial that is accessed more than once.

What is the difference between bacteriostatic water and sterile water?

Bacteriostatic water contains 0.9% benzyl alcohol as a preservative. Sterile water contains no preservative.

How much benzyl alcohol is in bacteriostatic water?

0.9%, which is 9mg of benzyl alcohol per millilitre.

What is 0.6% acetic acid used for in a laboratory?

It is a mildly acidic solvent used for materials that dissolve less readily in water at near-neutral pH.

Is “bac water” the same as bacteriostatic water?

Yes. “Bac water” is a common abbreviation for bacteriostatic water.

All Ascend Research products are sold strictly for laboratory research use only. They are not for human or animal use, and nothing in this article is medical advice.

The Ascend Research team