A Certificate of Analysis is the single most useful document a peptide supplier can give you — and one of the most commonly misunderstood. A CoA is only as valuable as your ability to read it. Here's what the sections mean and how to tell a real one from window dressing.
What a CoA actually is
A CoA is a report from a testing laboratory certifying that a specific batch of material was analysed and met certain specifications at the time of testing. The key word is batch: a genuine CoA is tied to a particular production lot, not to the product in general. If a certificate doesn't reference a specific batch number, it's not telling you much.
The sections that matter
- Product & batch reference. The compound name and the batch/lot number. This should match the number printed on the vial you receive.
- Purity result. Usually expressed as a percentage from an HPLC (high-performance liquid chromatography) analysis — commonly reported as RP-HPLC. This tells you how much of the sample is the target compound versus impurities.
- Identity confirmation. Often by mass spectrometry (LC-MS or MS). This confirms the sample actually is the compound it claims to be, by matching its molecular weight. Purity without identity is only half the picture.
- Method & conditions. Good certificates state the analytical method (e.g. "RP-HPLC, C18 column, detection at 214 nm"). It signals the testing was done to a defined standard rather than asserted.
- Testing lab & date. An independent third-party lab and a certification date. "Certified at the time of analysis" is the honest framing — it describes the batch as tested, on that date.
Purity and identity are not the same thing
This is the point most people miss. A high purity number tells you the sample is clean. The identity test tells you it's the right molecule. You want both. A supplier that shows a purity figure but no identity confirmation is only answering one of the two questions that matter.
How to verify a certificate is genuine
The strongest CoAs are independently verifiable. Many testing labs issue a report number and an access or verification code so anyone can confirm the certificate on the lab's own website. If a CoA carries a verification code, use it — it's the difference between "here's a PDF" and "here's a document you can independently check."
Be wary of certificates with no batch number, no named lab, no method, or no way to verify. Any of those on their own is a reason to ask questions.
See real examples
The best way to get comfortable reading a CoA is to look at real ones. Our CoA Library lets you open the actual certificates for tested batches — including the purity result, identity confirmation and the lab's verification details — so you can see exactly what a complete certificate looks like.
All products are supplied strictly for laboratory and in-vitro research use only. Not for human or veterinary consumption. This article is general information about laboratory documentation and is not medical or veterinary advice.