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 0.94%.
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 pH 5.4 on the independent laboratory's 2026-09-26 re-test (Freedom Diagnostics, accession 2609240374).
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 the actual measured purity; lot 25-1042-A measured 99.82% purity by HPLC-UV.
What is the preservative concentration in cheap bacteriostatic water?
BAC Water Depot’s bacteriostatic water contains 0.9 % w/v benzyl alcohol as the preservative. The product is a clear, colorless solution of water for injection plus this single preservative, meeting USP specifications. No other additives, buffers, salts, or colorants are present.
What preservatives are in BAC Water Depot’s bacteriostatic water?
The only preservative in BAC Water Depot’s bacteriostatic water is benzyl alcohol at 0.9 % w/v. This pharmaceutical‑grade aromatic alcohol provides the bacteriostatic effect required for multi‑dose use. No additional preservatives or excipients are included.