Bacteriostatic Water
USP-grade sterile water with 0.9% benzyl alcohol preservative for multi-dose reconstitution of lyophilized research peptides
About Bacteriostatic Water
Bacteriostatic Water for Injection (USP) is sterile, non-pyrogenic water for injection containing 0.9% (9 mg/mL) benzyl alcohol as a bacteriostatic preservative. Unlike sterile water for injection, the bacteriostatic preservative permits multi-dose use over up to 28 days after first puncture, making it the standard reconstitution solvent for lyophilized research peptides.
Bacteriostatic Water for Injection is a long-standing USP (United States Pharmacopeia) compendial product, specified for use as a sterile diluent and reconstitution solvent in laboratory and pharmaceutical contexts. The product consists of water for injection (highly purified, sterile, and non-pyrogenic) with the addition of benzyl alcohol at 0.9% w/v as a preservative.
The 0.9% benzyl alcohol concentration was selected based on extensive pharmaceutical compatibility research dating back to the early 20th century. At this concentration, benzyl alcohol provides effective bacteriostatic activity—preventing bacterial growth in the vial after needle puncture—while remaining compatible with most peptides, proteins, and small-molecule compounds used in research applications.
Bacteriostatic water has become the standard reconstitution solvent for lyophilized research peptides specifically because it permits the multi-dose use pattern common in research workflows. A typical 5 mg or 10 mg peptide vial may be reconstituted once and then drawn from across multiple research aliquots over several days; the bacteriostatic preservative makes this workflow safe and reproducible.
Quick Facts
| CAS Number | 7732-18-5 |
|---|---|
| Molecular Formula | H₂O (with 0.9% benzyl alcohol C₇H₈O preservative) |
| Molar Mass | 18.02 g/mol (water) |
| Sequence | Not applicable (solvent) |
| Form | Sterile liquid (6 mL / 10 mL multi-dose vial) |
| Grade | USP compendial (Bacteriostatic Water for Injection) |
| Preservative | 0.9% (9 mg/mL) benzyl alcohol |
| Sterility | Terminally sterilized, non-pyrogenic |
| pH | 5.0 – 7.0 |
| Container | Multi-dose glass vial, rubber stopper, flip-off cap |
| In-Use Period | Up to 28 days after first puncture |
| Shelf Life | 2 years unopened (room temperature) |
| Price (from) | $15.00 USD |
| SKU | PF-BACWATER |
How Bacteriostatic Water Works
Bacteriostatic water functions through the antimicrobial activity of its benzyl alcohol preservative, which inhibits bacterial growth without killing existing microorganisms. The product is manufactured to USP standards for sterility, purity, endotoxin content, and preservative concentration.
Benzyl Alcohol Bacteriostasis
Benzyl alcohol at 0.9% concentration disrupts bacterial cell membrane integrity, inhibiting bacterial growth and reproduction. This bacteriostatic (growth-inhibiting) activity differs from bactericidal (killing) action—the preservative prevents new bacterial colonization but does not sterilize an already-contaminated vial.
Multi-Dose Use
Unlike sterile water for injection, which must be discarded after a single use, bacteriostatic water can typically be used over up to 28 days after first puncture under controlled storage conditions. This makes it the preferred solvent for research workflows requiring multiple aliquots from a single peptide vial.
USP Compendial Standards
USP-grade bacteriostatic water is manufactured to strict pharmaceutical standards including sterility (terminal sterilization), apyrogenicity (low endotoxin), and preservative concentration. These standards ensure consistent quality across batches for research applications requiring traceable reagent provenance.
Reconstitution of Lyophilized Peptides
Lyophilized (freeze-dried) research peptides are typically reconstituted by injecting the desired volume of bacteriostatic water through the vial septum and gently swirling—not shaking—to dissolve the peptide. The resulting solution should be stored refrigerated and used within the timeframe specified for each peptide.
Frequently Asked Questions
- What is Bacteriostatic Water?
- Bacteriostatic Water for Injection (USP) is sterile, non-pyrogenic water for injection containing 0.9% (9 mg/mL) benzyl alcohol as a bacteriostatic preservative. Unlike sterile water for injection, the bacteriostatic preservative permits multi-dose use over up to 28 days after first puncture, making it the standard reconstitution solvent for lyophilized research peptides.
- What is the CAS number for Bacteriostatic Water?
- The CAS number for Bacteriostatic Water is 7732-18-5.
- What quality standard does Peptide Foundry's Bacteriostatic Water meet?
- Peptide Foundry's Bacteriostatic Water is USP-grade Bacteriostatic Water for Injection, manufactured to United States Pharmacopeia compendial specifications. Each lot is terminally sterilized, non-pyrogenic, and contains 0.9% (9 mg/mL) benzyl alcohol as a bacteriostatic preservative. Standards covered include sterility, apyrogenicity (low endotoxin), preservative concentration, and pH (5.0–7.0). HPLC purity testing applies to peptide active ingredients and is not used to characterize water; quality for BWFI is verified against the USP monograph rather than HPLC.
- How should Bacteriostatic Water be stored?
- Store unopened vials at controlled room temperature (15–25 °C / 59–77 °F), away from direct sunlight, and do not freeze. Shelf life is 2 years from manufacture when unopened. After first puncture, refrigerate (2–8 °C / 36–46 °F) and use within 28 days; always draw with sterile technique and discard if the solution becomes cloudy, discolored, or shows visible particulates.
- Does Bacteriostatic Water ship with a Certificate of Analysis?
- Bacteriostatic Water ships with lot-level release documentation confirming USP compliance: sterility, endotoxin limits, benzyl alcohol concentration, and pH. Because this is a USP compendial solvent rather than a peptide, the associated testing set differs from the HPLC / LAL / ICP-MS panel used for peptide active ingredients.
- Is Bacteriostatic Water sold for human use?
- No. All products sold by Peptide Foundry are strictly for in-vitro research and laboratory use only (RUO). They are not intended for human or animal consumption, therapeutic use, or diagnostic application.
Scientific References
- United States Pharmacopeia. Bacteriostatic Water for Injection (USP monograph). USP-NF.
- Pirnay JP, et al. Compatibility of antimicrobial preservatives with parenteral drug formulations. Int J Pharm. 2018;547(1-2):665-680.
- Strickley RG. Solubilizing excipients in oral and injectable formulations. Pharm Res. 2004;21(2):201-230. PubMed: 15032302
This product is sold strictly for in-vitro research use only (RUO). It is not intended for human or animal consumption, therapeutic use, or diagnostic application.