A clear research comparison: when to choose bacteriostatic water versus sterile water for reconstituting lyophilised peptides in the lab.
Which water should your lab use?
When reconstituting lyophilised research peptides, the solvent is part of experimental control. The two most common aqueous options are bacteriostatic water and sterile water. Both are used in laboratory settings; they are not interchangeable for every protocol.
This comparison is for research planning only. Products from My UK Peptides are for laboratory use — not for human or veterinary use.
Bacteriostatic water
Sterile water containing a preservative (commonly 0.9% benzyl alcohol). The preservative helps limit microbial growth after the vial stopper has been punctured, which is why many researchers prefer it when a reconstituted vial will be accessed more than once under controlled lab practice.
Sterile water
Water that has been sterilised but typically contains no bacteriostatic preservative. Once opened and accessed, contamination risk rises faster than with bacteriostatic water. Many protocols treat sterile-water reconstitutions as short-window or single-session preparations unless institutional rules say otherwise.
Side-by-side comparison
| Factor | Bacteriostatic water | Sterile water |
|---|---|---|
| Preservative | Usually yes (e.g. benzyl alcohol) | No |
| Multi-access vials | Often preferred | Higher contamination risk |
| Typical lab use case | Reconstituted stock drawn over several sessions | Short-window or single-session work |
| Assay caveats | Confirm preservative is compatible with your method | No preservative interference, shorter hold time |
Research tip: Always follow your institutional protocol. If your assay is sensitive to benzyl alcohol, sterile water (or another approved solvent such as dilute acetic acid for poorly soluble sequences) may be required instead.
Practical recommendation
- Default for many multi-access research reconstitutions: bacteriostatic water
- Preservative-sensitive assays or very short hold times: sterile water (with strict aseptic technique)
- Poorly soluble peptides: see acetic acid guidance on our reconstitution resources
Lab supplies at My UK Peptides
We supply bacteriostatic water and related laboratory reconstitution materials alongside research peptides on myukpeptides.com. For a fuller solvent overview, see our guide on bacteriostatic water for peptide reconstitution. Research use only.