Bacteriostatic Water

How It Works

Bacteriostatic water (BAC water) is sterile water containing 0.9% benzyl alcohol as a preservative. The benzyl alcohol inhibits bacterial growth, making it safe to use the same vial multiple times over up to 28 days after opening. This is critical for peptide research because most peptide vials contain multiple doses. When BAC water is added to a lyophilized peptide, it reconstitutes the powder into a solution that can be accurately dosed. Without the bacteriostatic agent, each vial puncture risks introducing bacteria that could contaminate the solution. BAC water vs. sterile water vs. bacteriostatic sodium chloride: Use BAC water as the default for peptide reconstitution. Use sterile water only for single-use applications or when benzyl alcohol sensitivity is a concern. Use bacteriostatic sodium chloride (0.9% NaCl with benzyl alcohol) when isotonicity is required. For step-by-step reconstitution instructions, use our reconstitution calculator at /tools/reconstitution-calculator.

Key Benefits

Research Highlights

• Benzyl alcohol at 0.9% concentration effectively prevents bacterial proliferation for up to 28 days (USP <797> guidelines)

• Standard reconstitution solvent recommended in peptide research protocols worldwide

• Step-by-step reconstitution: clean vial tops with alcohol swabs, inject BAC water slowly against the vial wall, gently swirl (never shake) until fully dissolved

• Common mistakes: using tap or distilled water (non-sterile), shaking the vial (denatures peptides), reusing BAC water beyond 28 days, storing at room temperature after opening

• Storage: unopened vials stable at room temperature (15-25°C). After first puncture, refrigerate at 2-8°C and discard after 28 days

• Bacteriostatic water is available from peptide suppliers, compounding pharmacies, and medical supply stores — always verify USP grade and 0.9% benzyl alcohol concentration