A Certificate of Analysis — a COA — is the single document that turns a purity claim into a testable fact. Every batch we release carries one, and every batch page and product listing on this site links back to it. This article walks through what's actually being measured, in plain terms, so the document is legible rather than decorative.
It's tied to a batch, not a product
The most important thing to understand about a COA is what it doesn't cover: the product line in general. A Certificate of Analysis documents one specific manufacturing run — a batch, identified by a lot number and a test date. Two vials of the same compound from two different batches can carry two different certificates, because they were tested separately, on different days, by an independent laboratory.
This is why the batch code printed on your vial matters. When you request a COA, quoting that code is what lets us hand you the certificate that actually corresponds to the material in your hand — not a generic specification sheet for the product as a category.
Purity (HPLC)
The headline figure on most certificates is a purity percentage, and it's produced by high-performance liquid chromatography (HPLC). In simple terms, HPLC separates a dissolved sample into its individual components as they pass through a column, then measures how much of the total signal corresponds to the target compound versus everything else — residual solvents, related substances, degradation products.
A result of 99.8%, for example, means that within the resolution of the method, 99.8% of the detected signal matches the target peptide against a certified reference standard. It's a chromatography result, not a subjective grade — which is exactly why it's reproducible and worth checking.
Identity confirmation
Purity alone doesn't confirm you're holding the right molecule — a sample could be highly "pure" and still be the wrong compound entirely. That's what identity confirmation is for. Depending on the lab and the compound, this typically means mass spectrometry or an equivalent analytical technique that confirms the measured molecular mass matches the expected sequence.
A complete COA reports both: purity (how clean the sample is) and identity (that it's the compound it claims to be). Either figure without the other leaves a gap.
Reading the document
When you open a Certificate of Analysis, look for four things:
- Batch or lot number — should match the code on your vial label.
- Test date — when the batch was actually analysed, not when the product line was first developed.
- Purity result — the HPLC figure, ideally with the method or reference standard noted.
- Testing laboratory — an independent third party, separate from manufacturing.
If any of these are missing, it's worth asking for clarification before treating a figure as reliable.
Every compound in our catalogue carries a batch-specific COA. You can look up the current purity result for any product, or request the full certificate, on our Certificates of Analysis page.