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Bacteriostatic Water for Peptide Reconstitution: The Complete Research Guide
Bacteriostatic water is sterile water for injection with 0.9% benzyl alcohol added as a preservative. That preservative is the whole point — it lets a vial be punctured and drawn from repeatedly, which is why it is the default solvent for turning a freeze-dried research-peptide cake back into a usable solution. Below: what it is, how it differs from sterile water, exactly how much to add, and how to store it.
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What bacteriostatic water actually is
Bacteriostatic water for injection is water manufactured to USP sterility standards with 0.9% (v/v) benzyl alcohol added. Benzyl alcohol is bacteriostatic — it stops bacteria from replicating — so the solution resists contamination across multiple needle punctures. Plain sterile water offers no such protection. That single difference is what makes bacteriostatic water the standard solvent for multi-dose research vials.
Sterile base
Water for injection, filtered and sterilised to pharmacopoeia grade before the preservative is added.
0.9% benzyl alcohol
The preservative that inhibits bacterial growth so the vial survives repeated punctures.
Multi-use vial
Typically supplied in 10 mL or 30 mL sealed vials for laboratory reconstitution work.
Bacteriostatic vs sterile water
For almost all research-peptide work the answer is bacteriostatic water. Reach for preservative-free sterile water only when the protocol specifically needs to exclude benzyl alcohol. We break the comparison down fully in bacteriostatic water vs sterile water.
How much bacteriostatic water do I add?
This is the question everyone asks, and the key insight is: the volume of water sets the concentration, not the amount of compound. The mass of peptide in the vial is fixed; adding more or less water just makes the solution more dilute or more concentrated.
Choose a volume that puts your intended measurements on easy-to-read syringe markings, then let our reconstitution calculator do the arithmetic. For the full worked method see how much bacteriostatic water to add.
Reconstitution technique in brief
The full step-by-step technique — equipment, angles and troubleshooting cloudy solutions — lives in our reconstitution guide.
Storage and shelf life
Unopened bacteriostatic water is fine at room temperature until its labelled expiry. Once you have punctured it, refrigerate at 1–6 °C and treat it as good for roughly 28 days — the window the benzyl alcohol reliably protects. The reconstituted peptide solution should also be refrigerated and shielded from light. See shelf life & storage for the detail.
Where to get it
New-U supplies bacteriostatic water (and preservative-free sterile water) as a reconstitution solvent alongside the research-peptide catalogue, so the compound and its solvent can be sourced together — all for laboratory research use only. Full sourcing detail is in where to buy bacteriostatic water.
Research peptides + reconstitution solvent, lab-direct
New-U supplies >99% HPLC-verified research compounds with a per-batch Certificate of Analysis, plus the bacteriostatic and sterile water to reconstitute them. Research use only — not for human consumption.
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Frequently asked questions
Sterile water for injection containing 0.9% benzyl alcohol as a preservative. The benzyl alcohol stops bacterial growth, which lets a vial be drawn from repeatedly — making it the standard solvent for reconstituting lyophilised research peptides. Research use only.
Both are sterile; only bacteriostatic water has the 0.9% benzyl alcohol preservative, so it stays usable for ~28 days across multiple punctures. Sterile water is single-use. For multi-dose research vials, bacteriostatic water is the usual choice.
The water sets the concentration, not the amount of compound: concentration (mg/mL) = vial mass (mg) ÷ water added (mL). A 5 mg vial + 2 mL = 2.5 mg/mL. Pick a convenient volume and use a reconstitution calculator. Laboratory preparation math only.
A 10 mg vial + 1 mL = 10 mg/mL; + 2 mL = 5 mg/mL. The water volume only changes concentration so syringe markings are easy to read — it does not change what is in the vial. Research preparation math only.
Unopened: room temperature until expiry. Opened: refrigerate at 1–6 °C and treat as good for ~28 days. After that, discard and use a fresh vial.
New-U Research Compounds supplies bacteriostatic water and preservative-free sterile water alongside its research-peptide catalogue, so you can source the compound and the solvent together. Provided strictly for laboratory research use.
All figures are laboratory-preparation reference points, not dosing guidance. New-U Research Compounds supplies bacteriostatic water and research compounds strictly for laboratory research use only — not for human consumption .
Research-grade · >99% HPLC purity · COA per lot
Buy Bacteriostatic Water from New-U Research Compounds
Lab-verified by Janoshik Analytical (RP-HPLC + ESI-MS), sealed vials, discreet tracked worldwide shipping. For laboratory research use only — not for human consumption.
Premium research peptides at >99% HPLC-verified purity, third-party tested by Janoshik Analytical with a Certificate of Analysis on every lot. Shipped lab-direct, discreet and cold-chain, worldwide. For laboratory research use only.
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[image: Bacteriostatic water research vial — USP-grade sterile water with 0.9% benzyl alcohol]