How to Read a Bacteriostatic Water COA (Certificate of Analysis)
By the BacWaterPep editorial team · Updated
Short answer. Check four things first: the lot number matches your vial, the benzyl alcohol content is a measured value inside 0.8–1.0%, sterility and endotoxin results are reported with their methods, and the dates are real calendar dates inside the shelf life.
| Lot | Same lot on COA, vial label and packing list |
|---|---|
| Benzyl alcohol | Measured % v/v, limit 0.9% ± 0.1% |
| pH | Measured value, limit e.g. 5.0–7.0 |
| Sterility | Membrane filtration, 'no growth' |
| Endotoxins | LAL, e.g. NMT 0.25 EU/mL |
| Particulates | Light obscuration counts ≥10 µm and ≥25 µm |
Step 1 — Is it your lot?
A COA proves something only about one lot. If the lot number is missing or different from your vial, the document does not apply to what you hold.
Step 2 — Numbers, not just 'pass'
Quantitative tests (benzyl alcohol, pH, endotoxins, fill volume, particulates) should show the measured value next to the limit.
Step 3 — The full test list
- Appearance and identity
- Benzyl alcohol content
- pH
- Elemental impurities
- Preservative effectiveness
- Fill volume
- Particulate matter
- Bacterial endotoxins
- Sterility
Red flags
- Impossible dates (one seller's page showed 31 February)
- The same results on every lot
- No method or no limit next to a result
- A laboratory or company name that does not match the seller
Sources
- DailyMed — Bacteriostatic Water for Injection, USP (0.9% benzyl alcohol), Hospira label
- CDC — Preventing Unsafe Injection Practices (multi-dose vials, 28-day rule)
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