Bacteriostatic water
Category: Supplies · Last updated
Bacteriostatic water (BAC water) is sterile water for injection containing 0.9% (w/v) benzyl alcohol as a bacteriostatic preservative. Sometimes labeled USP-grade sterile diluent in research-supply catalogs to avoid implying clinical use. It is the standard solvent for reconstituting lyophilized peptide research compounds.
Composition
- USP-grade Water for Injection
- 0.9% w/v Benzyl alcohol (preservative; bacteriostatic against gram-positive and gram-negative organisms, fungi)
- Sterile-filtered, gamma- or autoclave-sterilized, packaged in multi-use vials (typically 30 mL)
Why bacteriostatic vs. plain sterile water
Plain sterile water (USP "Sterile Water for Injection") permits microbial growth once the vial seal is breached for the first time. Bacteriostatic water suppresses microbial proliferation for the duration of the multi-use reconstitution window (typically 28 days at 2–8 °C).
Bacteriostatic saline (0.9% NaCl + 0.9% benzyl alcohol) is an alternative but introduces an osmolarity that can affect certain peptide solubilities; bacteriostatic water is the conservative default.
Storage
Sealed: 15–30 °C, stable until expiration date on the manufacturer label. Once accessed (first needle puncture): refrigerated 2–8 °C, use within 28 days.
See also
- Reconstitution · the procedure
- Storage · per-peptide reconstituted shelf-lives
- Sterile_technique