Name: Bacteriostatic Water 10mL
Brand: RetaLABS.is
SKU: bacteriostatic-water-10ml

Question 1

What is bacteriostatic water and why is it used for peptide reconstitution?

Accepted Answer

Bacteriostatic water is sterile water for injection containing 0.9% benzyl alcohol (9 mg/mL) as an antimicrobial preservative. The benzyl alcohol inhibits the growth of a broad spectrum of bacteria and fungi that could potentially contaminate the vial after the septum is first punctured, making it a multi-dose, multi-use diluent suitable for withdrawal over days or weeks. This property distinguishes it from sterile water for injection (SWFI), which contains no preservative and should be used immediately upon opening. For lyophilised peptide reconstitution, bacteriostatic water is the standard first-choice diluent because peptide research protocols typically involve multiple dose withdrawals from a single reconstituted vial over several weeks. It is isotonic at the benzyl alcohol concentration used, compatible with most peptides, and provides a stable reconstituted solution environment. The combination of sterility, multi-use capability, and broad peptide compatibility makes it the industry standard for laboratory-grade peptide reconstitution applications.

Question 2

How much bacteriostatic water do I need to reconstitute a peptide?

Accepted Answer

The volume of bacteriostatic water required depends entirely on the target concentration for your research protocol. The general formula is: volume (mL) = peptide mass (mg) ÷ desired concentration (mg/mL). For example, a 2 mg peptide vial with a target concentration of 1 mg/mL requires 2 mL; the same vial at 0.5 mg/mL requires 4 mL. For larger peptide vials such as 20 mg Retatrutide or 30 mg Tirzepatide, a working concentration of 5 mg/mL requires 4 mL or 6 mL respectively, both well within the capacity of a single 10 mL bacteriostatic water vial. A single 10 mL vial is therefore sufficient for reconstituting multiple peptide vials across a research protocol, reducing the need for multiple diluent vials and allowing batch reconstitution in a single session. See the Peptide Reconstitution Guide for concentration calculator tables and specific volume recommendations by product.

Question 3

How long does bacteriostatic water last once opened?

Accepted Answer

Once the septum of a bacteriostatic water vial is first punctured, the vial is considered stable for 28 days at room temperature (15–30°C). The 0.9% benzyl alcohol preservative maintains antimicrobial activity across this period, inhibiting the growth of common contaminant bacteria and fungi under normal laboratory conditions. This 28-day multi-use window is the standard established in pharmaceutical guidance for bacteriostatic water vials. After 28 days from first use, the vial should be discarded even if residual volume remains, as the ongoing integrity of the benzyl alcohol preservative cannot be reliably assumed beyond this period. During the 28-day window, maintain sterile technique with each withdrawal: use a clean syringe and needle for each draw, and do not contaminate the remaining contents with biological material from other vials. Store between 15–30°C and do not freeze. Mark the vial with the date of first use.

Question 4

Can bacteriostatic water be used with all peptides?

Accepted Answer

Bacteriostatic water is compatible with the large majority of research peptides, and is the standard recommended diluent for all lyophilised peptide vials in most research contexts. Exceptions include certain large proteins and growth factors where the benzyl alcohol preservative may influence protein conformation at higher concentrations. For very small peptides with high water solubility and no sensitive residues, bacteriostatic water dissolves them readily without compatibility concerns. Some peptides with known sensitivity to benzyl alcohol are better reconstituted in sterile water for injection or sterile PBS, however, these cases are comparatively rare and are typically noted in published protocols for those specific peptides. When the product-specific reconstitution guide does not specify otherwise, bacteriostatic water should be the default diluent choice: it provides the best combination of sterility assurance, multi-use utility, and peptide compatibility for standard research applications.

Question 5

Is the 10mL or 3mL vial better for research?

Accepted Answer

The 10 mL vial is more economical per millilitre and provides sufficient diluent volume to reconstitute multiple peptide vials across an entire research protocol without needing to replenish the bacteriostatic water supply. For researchers who regularly work with several peptide compounds or who run multi-week protocols, the 10 mL vial minimises interruptions and ensures consistent diluent supply from a single vial. The 3 mL vial is better suited to researchers working with a single peptide compound for a short protocol, or those who want a backup diluent supply that does not require committing to a large volume. Both vials contain the same bacteriostatic water formulation at the same 0.9% benzyl alcohol concentration and pH range. When deciding between the two, consider your total estimated bacteriostatic water usage across the full protocol: if you will use more than 2–3 mL, the 10 mL vial is the more practical choice.

Bacteriostatic Water 10mL

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