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How to read a certificate of analysis
A certificate of analysis is only useful if you know what it's supposed to contain. A purity number on its own, with no identity test, no lab name and no batch number, tells you almost nothing.
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In brief
Should you care? Yes, if you ever plan to check a product’s COA yourself rather than trusting a badge on the website. Most COAs shown to consumers are missing at least one of the things that actually make them meaningful.The short version
- Purity alone is not enough. You also need identity confirmation — proof it’s the right molecule, not just a pure one.
- It should be tied to a specific batch or lot number, not a generic “typical results” document.
- It should name the testing lab, so you could, in principle, call them.
What a real COA contains
| Element | Why it matters |
|---|---|
| Purity result (HPLC) | Tells you how much of the sample is the stated compound |
| Identity result (mass spectrometry) | Confirms it’s the right compound — see why this is different from purity |
| Batch or lot number | Ties the document to the specific unit you’re holding, not a generic average |
| Testing lab name | A real, named, independent lab — not "in-house testing" |
| Test date | Recent enough to be relevant to current stock |
The single most important line
If a COA shows only a purity percentage and nothing else, treat it as incomplete. Purity tells you how clean the sample is, not what the sample actually is. A wrongly-synthesised compound can still test as "99% pure" on an HPLC purity run if the test isn’t paired with an identity check. This is the single most common gap in COAs shown to consumers, and it’s the one most worth checking for.
Red flags on a COA itself
- No batch number, or a batch number that doesn’t match what’s printed on the product.
- "In-house testing" instead of a named independent laboratory.
- A PDF with no visible date, or a date far older than the product’s stated shelf life.
- Purity only, no identity test.
- A COA that can’t be looked up or verified — some independent labs let you check a report against their own records.
What we require before listing anything
This is exactly what the Register asks of anything we’d consider listing: a batch-linked COA, with both purity and identity, from a named independent lab. If a brand can’t produce that, it fails our standard — and we’d suggest applying the same bar yourself to anything you’re considering buying, from us or anyone else.
References
- US Pharmacopeia general chapters on peptide analysis: USP <1055> "Biotechnology-Derived Articles — Peptide Mapping" and USP <1060> "Mass Spectrometry-Based Multi-Attribute Method for Therapeutic Proteins" describe HPLC-based purity testing and mass-spectrometric identity confirmation as complementary, not interchangeable, methods. See usp.org/biologics/peptides.