What is Bacteriostatic Water?

Bacteriostatic water is sterile water containing 0.9% (weight/volume) benzyl alcohol as a bacteriostatic preservative. The benzyl alcohol inhibits bacterial growth, allowing multiple uses from a single vial over a period of days to weeks.

The preparation is manufactured according to pharmaceutical standards for sterility and purity. The water is processed through reverse osmosis, distillation, and terminal sterilisation, with the benzyl alcohol added under aseptic conditions.

For UK research laboratories, bacteriostatic water is an essential accessory for peptide reconstitution. It provides a sterile, preserved diluent that maintains peptide stability and prevents microbial contamination during repeated sampling.

Bacteriostatic water serves the following laboratory functions:

Peptide Reconstitution Diluent — The primary use of bacteriostatic water is as a diluent for lyophilised peptide powders. The sterile water rehydrates the peptide into a solution suitable for laboratory assays and administration.

Benzyl Alcohol Preservative — The 0.9% benzyl alcohol inhibits the growth of bacteria that may be introduced during vial sampling. This bacteriostatic action allows multiple withdrawals from a single vial over 14–28 days without significant microbial contamination risk.

pH Buffering — The water has a neutral pH (approximately 5.5–7.0), which is compatible with most peptides. The absence of buffers or additives means researchers can adjust pH as needed for specific assays.

Sterility Assurance — The terminal sterilisation process ensures the water is free of microorganisms, endotoxins, and particulate matter that could interfere with sensitive cellular or biochemical assays.

Bacteriostatic water is employed across multiple laboratory applications in UK research:

Peptide Reconstitution — The primary application is reconstituting lyophilised peptides at precise concentrations for laboratory use. The preserved formulation allows multiple uses from a single vial.

Dilution Series — Bacteriostatic water is used to create precise dilution series of peptide stock solutions for dose-response and concentration-dependence studies.

Vehicle Control — In cellular assays, bacteriostatic water serves as a vehicle control for peptide-treated samples. The minimal benzyl alcohol concentration does not affect cell viability at typical peptide volumes.

Sterile Technique Training — Bacteriostatic water is used in laboratory training for aseptic reconstitution technique, providing a safe medium for practicing sterile vial access and dilution protocols.

Buffer Preparation Base — The sterile, endotoxin-free water serves as a base for preparing custom laboratory buffers and solutions for peptide research.

Bacteriostatic water is supplied as a sterile liquid in sealed vials. No reconstitution is required — it is ready for immediate laboratory use:

• Storage: 2–8°C (refrigeration) or controlled room temperature (15–25°C)
• Shelf life: Use within 28 days of first vial puncture
• Single vial multiple use: The benzyl alcohol preservative allows multiple withdrawals over the 28-day period
• Visual inspection: Do not use if the solution is cloudy, discoloured, or contains visible particles
• Aseptic technique: Wipe the septum with 70% isopropyl alcohol before each withdrawal; use sterile needles and syringes

• Unopened vial: 2–25°C, protected from light
• Opened vial: 2–8°C (refrigeration recommended)
• In-use period: 28 days maximum after first puncture
• Discard: Any unused portion after 28 days or if contamination is suspected
• Do not freeze: Freezing may cause vial breakage and compromise sterility