Bacteriostatic Water (USP Grade)
The same diluent, held to a compendial standard and supplied by the ampoule.
Solutions & diluents · 4 min read · updated 13 Aug 2026
Research use only. The ranges below are what published studies and community protocols report. They are reference material for laboratory research, not medical advice or a recommendation for human or veterinary use.
The compound
Bacteriostatic Water (USP Grade)
View- Type
- Bacteriostatic Water (USP Grade)
- CAS
- 7732-18-5
- Formula
- H₂O / C₇H₈O
- Mass
- N/A
At a glance
- Composition
- Sterile water for injection + 0.9% benzyl alcohol, USP grade
- CAS (water)
- 7732-18-5
- What USP grade means
- Manufactured and tested against the United States Pharmacopeia monograph
- Format
- Sold per ampoule
- Size stocked
- 10 ml
Functionally this is the same solution as standard bacteriostatic water — sterile water with 0.9% benzyl alcohol — and everything in that article applies here unchanged: the same technique, the same 28-day preservative window, the same fill-volume arithmetic.
The difference is the standard it is held to. USP grade means the material is manufactured and released against the United States Pharmacopeia monograph, which specifies limits for particulates, endotoxin, pH, and identity and content of the preservative, with documented testing behind each. Non-compendial material may well meet the same limits; the difference is that USP grade is required to demonstrate it.
For research where the diluent is part of what is being controlled — anything with endotoxin-sensitive endpoints, or work that will be written up — the compendial grade is the defensible choice. For routine reconstitution, standard bacteriostatic water does the same job.
When the grade is worth paying for
- Endotoxin-sensitive work: cell culture, immunological endpoints, or anything where a pyrogen response would confound the result.
- Documented protocols: when the diluent needs a specification and a lot number that can be cited.
- Larger fill volumes: the higher the volume administered, the more any particulate or endotoxin burden matters.
- Long protocols with a single diluent vial in repeated use.
Why it is priced per ampoule
This item is stocked and priced by the ampoule rather than by the vial, which is why the catalogue shows it as "per ampoule" rather than "per vial". The unit is the container, and a single 10 ml ampoule covers several peptide reconstitutions.
Storage
- Unopened: room temperature, away from light.
- Opened: 2–8 °C, 28-day window.
- Discard if not clear and colourless.
Cautions
- The same benzyl alcohol considerations apply as for standard bacteriostatic water.
- USP grade describes the manufacturing and testing standard. It does not change the chemistry or extend the preservative window.
References & credit
- 1USP monograph — Bacteriostatic Water for Injection — The compendial standard the grade refers to.
This article was written in-house. Where a dose range reflects community practice rather than a published trial, the community references we consulted are credited above and the article says which is which.