Overview
Reconstitution is the step that turns a freeze-dried (lyophilized) peptide into a solution of known concentration. The solvent and the technique both matter for reproducibility. The wrong solvent can be incompatible with an assay system, and rough handling can denature or foam the peptide. An unrecorded volume makes every downstream concentration a guess.
What Bacteriostatic Water Is
Bacteriostatic water is sterile water containing 0.9% benzyl alcohol as a preservative. The benzyl alcohol inhibits microbial growth in the vial once its septum has been entered, which is what distinguishes it from plain sterile water. It contains no buffer and no salt.
| Solvent | Composition | Preservative | Typical laboratory note |
|---|---|---|---|
| Bacteriostatic water | Sterile water + 0.9% benzyl alcohol | Yes | Suited to a vial that will be entered more than once |
| Sterile water | Sterile water only | No | Intended for a single entry; discard the remainder |
| Sterile saline | 0.9% sodium chloride in sterile water | No (unless labeled bacteriostatic) | Used where the assay requires isotonic conditions |
The right choice depends on the assay system and the downstream methodology. Researchers should follow the buffer specifications in their target literature.
Volume and Concentration
Concentration is the vial’s mass divided by the volume of solvent added:
concentration (mg/ml) = vial content (mg) ÷ solvent volume (ml)
For example, a generic 10 mg vial reconstituted with 2 ml of solvent gives 5 mg/ml, and the same vial with 4 ml gives 2.5 mg/ml. More solvent lowers the concentration; less solvent raises it. Choosing a round volume is the simplest way to reach an easy-to-read concentration.
For the exact figures for each compound and vial size, use the Peptide Reconstitution Calculators. They take the vial size and the solvent volume as inputs and return the concentration. They never work backward from a target amount.
Laboratory Handling Technique
- Let the vial reach room temperature before opening it, to limit condensation on the solid.
- Wipe the septum with 70% isopropyl alcohol and let it dry.
- Add the solvent slowly down the inside wall of the vial, not directly onto the powder. This limits foaming and shear stress on the peptide chain.
- Do not shake. Swirl gently or let the vial stand until the solid has fully dissolved. A clear solution with no visible particles is the expected end state.
- Label the vial with the reconstitution date, the solvent, and the volume added.
Handling an Opened Vial of Bacteriostatic Water
The preservative slows microbial growth; it does not make an opened vial sterile indefinitely. Following USP practice for preserved multi-use containers, the common practice is to discard an opened vial 28 days after its septum is first entered, unless the manufacturer’s labeling states otherwise. The limit reflects the contamination risk of repeated entries through the septum. It is not a loss of the preservative itself.
Record the first-entry date on the vial, store it as its label directs, and discard it sooner if the solution becomes cloudy or shows particles.
Storage After Reconstitution
Storage conditions for the reconstituted peptide (temperature, light, aliquoting and freeze–thaw cycles) are covered in the Peptide Storage Guide.
Documentation
Solira’s bacteriostatic water is third-party tested for sterility (USP ⟨1223⟩). The report is published at Bacteriostatic Water lab results. Lot reports for every compound are listed on Testing.
Related Research
- Peptide Storage Guide — temperature, light and freeze–thaw handling for lyophilized and reconstituted peptides
- What Are Research Peptides? — beginner reference for researchers new to this category
- Reconstitution Supplies — bacteriostatic water in 3 ml and 10 ml vials
All products are sold for laboratory research use only, and are not for human, veterinary, or food use in any form.
