Composition & Specifications
Bacteriostatic Water Ingredients
Two ingredients: USP Water for Injection plus 0.9% w/v benzyl alcohol preservative. No additives, no salts, no buffers. pH 4.5–7.0. Per-lot HPLC-verified concentration documented on every BAC Water Depot Certificate of Analysis.
Direct Answer
Bacteriostatic water contains exactly two ingredients: Water for Injection (USP) and 0.9% w/v benzyl alcohol. Nothing else. The benzyl alcohol provides bacteriostatic (microbial growth inhibition) effect, enabling multi-dose use of a single vial for up to 28 days when refrigerated. BAC Water Depot publishes the actual HPLC-measured benzyl alcohol concentration on every per-lot CoA.
Full composition spec
| Component | Specification | Method |
|---|---|---|
| Water for Injection (USP) | ≥98% water | Karl Fischer titration |
| Benzyl alcohol | 0.9% w/v ± 5% | USP <621> HPLC-UV |
| pH | 4.5 – 7.0 | USP <791> potentiometric |
| Appearance | Clear, colorless, particulate-free | USP <790> visual |
| Bacterial endotoxin | ≤ 0.25 EU/mL | USP <85> LAL kinetic chromogenic |
| Sterility | No growth, 14-day | USP <71> membrane filtration |
| Particulates ≥ 10 µm | ≤ 6,000 / container | USP <788> light obscuration |
| Particulates ≥ 25 µm | ≤ 600 / container | USP <788> light obscuration |
Frequently Asked Questions
What are the ingredients in bacteriostatic water?
Bacteriostatic water contains two ingredients: (1) Water for Injection (USP) — purified water meeting USP monograph specifications, and (2) 0.9% w/v benzyl alcohol — a pharmaceutical-grade preservative that inhibits microbial growth. No other additives, no buffers, no salts, no colorants. The product is a clear, colorless solution at pH 4.5–7.0.
How much benzyl alcohol is in bacteriostatic water?
0.9% w/v (weight per volume) benzyl alcohol — 9 mg per mL. This is the USP-monograph concentration validated to provide antimicrobial effectiveness for multi-dose use over 28 days when refrigerated. BAC Water Depot's per-lot CoA documents the actual HPLC-measured concentration; lot 25-1042-A measured at 0.92% w/v.
What is benzyl alcohol and why is it in bacteriostatic water?
Benzyl alcohol is a pharmaceutical-grade aromatic alcohol used as a bacteriostatic preservative. It inhibits the growth of bacteria, yeast, and fungi at the 0.9% concentration. Including it as the preservative allows a multi-dose vial of water for injection to be punctured and drawn from multiple times over 28 days without microbial growth — the property that makes bacteriostatic water a multi-dose diluent.
Is bacteriostatic water just salt water?
No. Bacteriostatic water is water + benzyl alcohol preservative — no sodium chloride. The product with sodium chloride is called Bacteriostatic Sodium Chloride for Injection, which is 0.9% saline plus benzyl alcohol. They are different USP monographs and different products. BAC Water Depot sells Bacteriostatic Water for Injection, not the saline-containing variant.
Does bacteriostatic water contain any other additives?
No. USP-grade Bacteriostatic Water for Injection contains only Water for Injection and 0.9% benzyl alcohol. No buffers, no salts, no sugars, no colorants, no flavors. The minimal composition is part of what makes it suitable as a research peptide diluent — the only compatibility consideration is benzyl alcohol itself.
What is the pH of bacteriostatic water?
The USP monograph specifies pH 4.5–7.0 for Bacteriostatic Water for Injection. BAC Water Depot's per-lot CoA documents the actual measured pH; lot 25-1042-A measured at pH 5.6. pH is verified per lot via USP <791> potentiometric method.
What is the water purity in bacteriostatic water?
The Water for Injection component is ≥98% water by Karl Fischer titration once the 0.9% benzyl alcohol is accounted for, with conductivity, total organic carbon, and microbial limits meeting the USP monograph for Water for Injection. BAC Water Depot's per-lot CoA reports actual measured water content; lot 25-1042-A measured 99.05% water content.
