How to read a certificate of analysis
A COA is the receipt for a claim. For bacteriostatic water, five lines tell you almost everything — here's what each one means and the value a clean lot should show.
A certificate of analysis (COA) is a lab's signed report on a specific batch. Anyone can print "sterile" on a label; a COA is a third party putting a number behind it. The catch is that a COA only means something if it's tied to your lot number and comes from an accredited lab — so before you decode the tests, check those two things.
First, two checks before you read a single result
1Does the lot match? The lot on the certificate must match the lot stamped on your vial. A COA for a different batch is marketing, not evidence.
2Who signed it? Look for an ISO 17025–accredited laboratory. That accreditation is what makes the numbers defensible rather than self-reported.
A sample certificate
Here's the shape of a clean report. Each row below the header is a test, its method, and its result.
Line by line
- Sterility — USP <71>
- The direct test of whether viable microorganisms grew from a sample of the batch. This is the headline result: for a product sold as sterile, it should read PASS, full stop. There is no "mostly."Want to see: PASS
- Bacterial endotoxin — USP <85>
- Endotoxins are fragments left behind by bacteria. They survive sterile filtration (they're far smaller than the 0.2 µm a filter catches), so a separate test matters. Results are reported in endotoxin units per millilitre (EU/mL); lower is better, and you want a figure comfortably below the relevant limit.Want to see: a low number, e.g. < 0.25 EU/mL
- Benzyl alcohol — assay
- This confirms the preservative is actually present at the stated strength. For bacteriostatic water that's 0.9% w/v; a small tolerance around it (say 0.89–0.91%) is normal batch variation. Too low and the preservative can't do its job; the assay is what proves the label.Want to see: ≈ 0.90% w/v
- pH — USP <791>
- How acidic or basic the solution is. Bacteriostatic water typically sits mildly acidic, around pH 5. A value far outside the expected range is a flag that something in compounding drifted.Want to see: within the stated range, ~5.0
- Particulate matter — USP <788>
- Checks for visible and sub-visible particles in the solution. A clean lot conforms to the particulate limits — meaning nothing is floating that shouldn't be.Want to see: Conforms
Red flags: a COA with no lot number, no lab name or accreditation, no test methods listed, or a "sterility" line reported as anything other than a clear pass. Vague is a choice.
The point of all this
A COA turns "trust us" into "here are the numbers, from a lab that isn't us, for the batch you're holding." That's the whole reason to prefer a seller who publishes one per lot. When you can match the number on your vial to a signed report, you're not buying a brand — you're buying a verified batch.
Every unasolution lot ships with its COA
Look up any lot — or scan the QR on the vial — and read the full result before you buy.
For laboratory and research use only. This article is general educational information, not medical, veterinary or professional advice. Values described are illustrative of a typical clean lot, not specifications or guarantees. unasolution products are not drugs and are not for human or veterinary use; no medical or therapeutic claims are made.