Bacteriostatic water is the most commonly used solvent for reconstituting lyophilized peptides in the laboratory. This guide explains its composition, how it differs from sterile water and saline solution, its shelf life, and what Janoshik measured in our batch.
Bacteriostatic water 3 ml – €5See the Janoshik report
The essentials
What it contains
Just two ingredients:sterile waterand of thebenzyl alcoholat 0.9%. Benzyl alcohol (C7H8O, CAS No. 100-51-6) is a common preservative in multidose bottles. At this concentration, it isbacteriostaticIt prevents bacteria from multiplying, without claiming to sterilize an already contaminated solution. This is why hygiene rules during sampling remain essential.
The bottle is closed by aseptuma rubber stopper that the needle passes through without opening the bottle. Outside air therefore does not enter, and the preservative protects the contents between two uses.
Sterile water, physiological saline: the differences
| Solvent | Composition | Conservative | Opened bottle |
|---|---|---|---|
| SolventBacteriostatic water | CompositionSterile water + 0.9% benzyl alcohol | ConservativeYes | Opened bottleUp to 28 days in the refrigerator |
| SolventSterile water | CompositionSterile water only | ConservativeNo | Opened bottleUse only, immediately after opening |
| SolventPhysiological saline | CompositionWater + sodium chloride 0.9% | ConservativeNo | Opened bottleUse only, immediately after opening |
The figure "0.9%" is misleading: in physiological saline, it's salt (sodium chloride), not a preservative. Therefore, physiological saline is not a substitute for bacteriostatic water in a bottle that is repeatedly pierced.
Simple sterile water is suitable when the entire solution is used at once. However, when a reconstituted bottle is used over several days, bacteriostatic water is the usual choice for laboratories.
What is it used for in the laboratory?
A lyophilized peptide is delivered in powder form, the form that keeps it stable. To study it, it must be reconstituted in solution: this is thereconstructionBacteriostatic water is added slowly along the side of the powder bottle, then the bottle is gently rotated without shaking. The complete method, from septum cleaning to storage, is described inreconstitute a lyophilized peptide.
The volume of water depends on the desired concentration for the experiment. A 3 ml bottle can be used to reconstitute one or more peptide bottles, depending on the volume chosen for each.
Storage, before and after opening
| State | Où | Duration |
|---|---|---|
| StateSealed bottle | OùRoom temperature, away from light | DurationUntil the date indicated on the label |
| StateOpened bottle of water | OùRefrigerator (2 to 8 °C) | DurationUp to 28 days after the first sample |
| StatePeptide reconstituted with this water | OùRefrigerator (2 to 8 °C), never in the freezer | DurationUp to 28 days, depending on the peptide |
Note the date of the first sample on the bottle. Discard the water if it becomes cloudy, if particles appear, or if the expiration date has passed. For the storage of the peptides themselves, seeconservation of retatrutide.
Our Janoshik analysis
| Report | Batch | Analysis | Benzyl alcohol measured | Key |
|---|---|---|---|---|
| Report#229270 | BatchMP-777BA3101 | Analysis10/09/2026 | Benzyl alcohol measured8.41 mg/ml | KeyQWLNKTJBHLDS |
We had the bacteriostatic water analyzed, as well as the peptides. Janoshik measured 8.41 mg/ml of benzyl alcohol, with a nominal concentration of 9 mg/ml (0.9%). The key can be verified at janoshik.com/verify: the original report is available on the lab's website. The batch number is printed on the bottle.
Where to find it at PeptiLine
| Product | Content | Price |
|---|---|---|
| ProductBacteriostatic water 3 ml | Content1 x 3ml bottle with septum | Price5 € |
| ProductReenactment Pack | Content1 x 3ml water, 1 x reconstitution syringe, 10 x 31G syringes, gloves, swabs | Price14,90 € |
| ProductR10 Pack | ContentRetatrutide 10 mg with bacteriostatic water and equipment | Price69,90 € |
Frequently Asked Questions
What is bacteriostatic water?
It is sterile water with 0.9% benzyl alcohol added, a preservative that inhibits bacterial growth. It is used to reconstitute lyophilized peptides in the laboratory.
What is the difference between bacteriostatic water and sterile water?
Sterile water contains no preservatives: once the bottle is opened, it must be used immediately. Bacteriostatic water contains benzyl alcohol, which allows an opened bottle to be kept for up to 28 days in the refrigerator.
Can saline solution be used instead?
Not for a bottle that has been drawn from multiple times. The 0.9% physiological saline is sodium chloride, not a preservative: the solution is not protected after opening.
How long can bacteriostatic water be stored?
Sealed, until the date indicated on the label, at room temperature and away from light. Once opened, for up to 28 days in the refrigerator after the first use.
How much does bacteriostatic water cost at PeptiLine?
The 3 ml bottle costs €5. It is also included in the Reconstitution Pack (€14.90) and in retatrutide packs. Batch MP-777BA3101 was analyzed by Janoshik (report #229270).
- Bacteriostatic water: the guide— composition, sterile water, preservation, analysis (you are here)
- Reconstitute a lyophilized peptide— the step-by-step manipulation in the laboratory
- Retatrutide conservation— powder, reconstituted solution and transport
- Bacteriostatic water 3 ml— septum vial, Janoshik report #229270
- Reenactment Pack— water, syringes, gloves and tampons
- Kit retatrutide— packs with bacteriostatic water included
- Certificates of analysis— all the Janoshik reports, with their key
Monograph "Bacteriostatic Water for Injection" (USP); 28-day rule for multidose vials (USP); PubChem CID 244 (benzyl alcohol); Janoshik report #229270. PeptiLine products are intended for scientific laboratory research use only. This page does not provide medical advice, protocols, or dosage information.