Documentation
How to Read a Certificate of Analysis
A Certificate of Analysis (COA) is the one document that actually tells you what's in the vial — not what the label says, not what the product page claims, but what an independent lab measured. If you're sourcing research material from anywhere, reading a COA properly is the single most useful skill you can have. Here's what each section actually means.
1. Identity testing
Before purity even matters, the lab needs to confirm the sample is the compound it claims to be. This is usually done by LC-MS (liquid chromatography–mass spectrometry), which measures molecular weight and fragmentation pattern against a reference standard. A COA without identity confirmation — only a purity number — hasn't actually proven you're holding what the label says.
2. Purity, and what percentage actually means
Purity is almost always reported from HPLC (high-performance liquid chromatography), expressed as a percentage at a specific detection wavelength (commonly 214nm or 220nm for peptides). A few things worth knowing:
- The wavelength matters. Different wavelengths can give slightly different readings on the same sample — it's not dishonest, just a detail worth noticing if you're comparing two COAs from different labs.
- Purity isn't the same as identity. A sample can be 99% "pure" and still be the wrong compound if identity testing wasn't done separately.
- Watch for stated vs. tested amounts. A legitimate COA reports the actual measured content, which can differ slightly from the labeled amount — that's normal; what's not normal is no measured content being reported at all.
3. Lot number and batch-specificity
Every real COA is tied to a specific lot or batch number — not a generic "this is what our product typically tests at" document. If a vendor only has one COA PDF that gets reused across every order regardless of when it shipped, that's a sign the testing isn't actually tracking what's currently in stock.
4. Testing lab and independence
The COA should name the actual third-party lab that performed the testing — not just "independently tested" with no lab named. A named, findable lab means the results are at least theoretically checkable and the vendor has something to lose by faking them.
Some vendors go further and keep a running library of every batch's COA, searchable by lot number, rather than a single PDF per product. DAAVY Research's COA library is a decent example of this — every product links to its specific batch documentation rather than one generic file standing in for all of them.
5. What a COA can't tell you
A clean COA confirms identity and purity at the time of testing — it says nothing about storage conditions after that point, how the material was handled in transit, or anything about outcomes. Treat it as one input into your own evaluation, not a guarantee.
Want the storage & handling guide too?
A short reference on reconstitution, temperature stability, and shelf life — the natural follow-up to understanding a COA.
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