A certificate of analysis is a one-page document with maybe a dozen fields on it. Most people glance at the purity number and close the tab, which is a shame, because the purity number is one of the least informative things on the page.
Here’s what each field is doing, in the order you’ll usually meet it.
The header
Testing laboratory. Start here, not at the purity figure. Is a laboratory named, with a legal entity and contact details? An unnamed lab, or a certificate on the seller’s own letterhead with no third party mentioned, is a self-assessment. It might be perfectly accurate. It just isn’t independent, and independence is the entire reason the document exists.
Report or certificate number. A unique identifier the lab can look up. It’s what makes the document checkable rather than decorative.
Date of analysis. Note this and compare it to when the lot was produced. A certificate from long before the batch was made isn’t describing your batch.
Sample identification
Compound name. Should match the product exactly.
Lot or batch number. The single most important field, and the one people skip. This number must match the number printed on the vial in your hand. If it doesn’t, the certificate describes material you don’t have. A vendor showing one “representative” certificate for a product they’ve restocked six times is showing you a document about a batch that’s long gone.
Appearance. Usually “white lyophilized powder.” Low information, but a mismatch is worth asking about.
The results
Purity, with a method. Typically HPLC-UV, given as a percentage. The method matters as much as the number — a percentage with no method attached is a number someone typed. What HPLC actually measures is here.
Identity, with a method. Usually mass spectrometry, reported as “confirmed” or “conforms,” sometimes with theoretical and observed mass side by side. If identity is absent entirely, the certificate never established that the vial contains the labeled compound at all.
Net peptide content. How much of the powder is peptide, as opposed to counter-ion salt and residual water. Frequently missing, because it’s the less flattering figure. Why the gap matters is here.
Conclusion. Pass, fail, or conforms. Read it. It’s the lab’s actual verdict rather than your interpretation of the numbers above it.
Four ways a certificate can look fine and mean nothing
- The lot number doesn’t match your vial. The most common issue by a wide margin, and usually not deliberate — it’s just easier to host one PDF than to test every batch.
- No laboratory is named. A logo isn’t a name. Look for a legal entity you could contact.
- Purity only, no identity. Confirms the material is clean. Says nothing about what it is.
- An image instead of a document. A screenshot or cropped JPEG on a product page is a picture of a certificate. Ask for the PDF.
Try it on ours
Take lot ML-001. The certificate names Freedom Diagnostics LLC as the testing laboratory, gives a report number, and lists HPLC-UV purity at 99.84%, identity confirmed by LC-MS, and net peptide content of 12.11 mg against a 10 mg label.
Every one of those fields is on the page for the same reason: so you can check the claim instead of taking our word for it. Pull the report and read it against this list.
All Molecula Labs products are supplied strictly for laboratory research use. Not for human or animal consumption. Not drugs, foods, cosmetics, supplements, or medical devices. Not evaluated by the FDA.