Bacteriostatic water is never cloudy when it is in good condition. Benzyl alcohol at 0.9% is fully dissolved and invisible, so any haze, turbidity or floating material means something has changed inside the vial. The correct response is the same whatever the cause: the vial is set aside, not used, and recorded against its lot number.
The three causes
| Cause | What it looks like | How it happens |
|---|---|---|
| Microbial growth | Uniform haze that develops over days in an opened vial, sometimes with strands or a film | Organisms introduced during a withdrawal have outgrown the preservative, usually because the vial was open too long, entered with poor technique, stored warm, or the preservative was diluted by something added to the vial |
| Precipitate | Cloudiness or particles appearing immediately or soon after something was added | A material dissolved in the water has come out of solution, or has reacted with benzyl alcohol or with the slightly acidic, unbuffered water. Bacteriostatic water itself does not precipitate |
| Compromised closure | Haze, particles or discoloration in a vial that has never been opened | A lifted crimp, cracked glass or damaged stopper has let the contents be contaminated in storage or transit |
What is not a cause
- Cold storage. Chilling does not make benzyl alcohol come out of solution at 0.9%, and condensation on the outside of a cold vial is not cloudiness inside it. Let the vial reach room temperature and look again.
- Air bubbles. Fine bubbles after handling rise and disappear within seconds. A haze that stays is not bubbles.
- Light or age alone. Oxidation of benzyl alcohol changes odor and ultraviolet absorbance, not visible clarity. See benzyl alcohol oxidation.
What to do
Do not filter, heat or otherwise try to rescue the vial. Quarantine it, note the lot number, the date it was opened and what, if anything, was added to it, and check other vials from the same lot. If an unopened vial is cloudy, contact the supplier with the lot number and photographs. See can bacteriostatic water go bad?, what color should it be? and what to do about a lot notice.
Preventing it
Choose a vial size that will be finished within 28 days, wipe the stopper before every entry, use a fresh sterile transfer device each time, keep the vial at 20–25 °C in its carton, and never add anything to a vial of bacteriostatic water that is meant to serve as a diluent for other work. See how many times can a vial be punctured? and common mistakes.
All BAC Water Supply products are supplied for laboratory research use only and are not for human or veterinary use.