What is Bacteriostatic Water?
Bacteriostatic water (BAC water) is sterile water containing 0.9% benzyl alcohol as a preservative. Unlike plain sterile water, BAC water inhibits bacterial growth, allowing multi-use over extended periods. This makes it ideal for reconstituting peptides that will be used over several weeks.
The benzyl alcohol doesn't kill bacteria outright — it prevents them from reproducing. This is called a "bacteriostatic" effect, as opposed to "bactericidal" (which kills bacteria directly).
Proper Storage
Before Opening
- Store at room temperature (15-30°C / 59-86°F)
- Keep away from direct sunlight
- Check expiration date before use
- Inspect for cloudiness, particles, or discoloration
After Opening
- Store in refrigerator (2-8°C / 36-46°F)
- Use within 28 days of first puncture
- Always use a sterile needle for each withdrawal
- Swab the rubber stopper with alcohol before each use
Never Freeze BAC Water
Freezing can affect the preservative concentration and sterility. BAC water should always be stored in liquid form.
Proper Withdrawal Technique
Step 1: Clean the Stopper
Wipe the rubber stopper with a 70% isopropyl alcohol swab. Let it air dry for 10-15 seconds.
Step 2: Use a Fresh Needle
Never reuse needles between vials. Each puncture through a rubber stopper can introduce contaminants and dulls the needle, making subsequent punctures more difficult.
Step 3: Avoid Coring
Insert the needle at a 45° angle, then straighten to 90° once through the stopper. This prevents "coring" — where a small plug of rubber is pushed into the vial.
Step 4: Equalize Pressure
Inject a volume of air equal to the water you plan to withdraw. This prevents creating a vacuum that makes withdrawal difficult.
When NOT to Use BAC Water
- For certain sensitive compounds — some biomolecules are sensitive to benzyl alcohol
- When immediate use is planned — if using entire vial in one session, sterile water is fine
- If visually contaminated — discard immediately if cloudy or particles visible