What Is Bacteriostatic Water?
Bacteriostatic water (BAC water) is sterile water that contains 0.9% benzyl alcohol as a preservative. The benzyl alcohol inhibits the growth of bacteria, making it safe for repeated use over multiple withdrawals — unlike plain sterile water, which should only be used once.
BAC Water vs. Sterile Water
| Feature | Bacteriostatic Water | Sterile Water |
|---|---|---|
| Preservative | 0.9% benzyl alcohol | None |
| Multi-dose use | Yes (up to 28 days) | No (single use only) |
| Bacterial inhibition | Yes | No |
| Shelf life after opening | ~28 days | Must be discarded immediately |
| Best for | Multi-dose peptide vials | Single-use applications |
Why BAC Water Is Preferred for Peptides
Most peptide research protocols involve drawing multiple doses from a single vial over days or weeks. Without a bacteriostatic agent, each needle insertion introduces a small risk of contamination. The benzyl alcohol in BAC water provides a critical safety layer by preventing bacterial proliferation.
How to Use BAC Water with Peptides
- Sanitize the rubber stoppers on both the BAC water and peptide vials with alcohol swabs
- Draw the calculated volume of BAC water using a sterile syringe
- Inject slowly into the peptide vial along the glass wall
- Swirl gently — never shake
- Store the reconstituted solution in the refrigerator
Storage Guidelines
- Unopened BAC water: Store at room temperature, away from light. Check the expiration date on the label.
- Opened BAC water: Refrigerate and use within 28 days. Mark the date you first pierced the stopper.
- Reconstituted peptides: Keep refrigerated at 36–46°F (2–8°C) and use within 30 days.
How Much BAC Water to Add
The volume of BAC water you add determines the concentration of your peptide solution. A common approach:
- For single-dose protocols: Use 0.5–1 mL for easy measurement
- For multi-dose protocols (20+ doses): Use 2–3 mL to allow for precise small-volume measurements
Use the formula: Concentration = Peptide Mass (mg) ÷ Volume of Water (mL)
Common Questions
Can I use regular water instead of BAC water?
No. Tap water and distilled water are not sterile and will introduce contaminants. Only use pharmaceutical-grade bacteriostatic water or sterile water for injection.
Does BAC water expire?
Yes. Check the manufacturer’s expiration date. After opening, use within 28 days.
Can BAC water be frozen?
It’s not recommended. Freezing may affect the preservative concentration and compromise sterility.
Conclusion
Bacteriostatic water is an essential supply for any peptide research protocol. Its preservative properties make it safe for multi-dose use, and when stored correctly, it helps maintain the stability and sterility of reconstituted peptides.
All products are intended for research purposes only.