How to read a peptide certificate of analysis
A certificate of analysis is a laboratory's record of what a specific batch contained. This is how to read one, section by section, and which four checks matter before you trust the number on the front.
Last updated 2026-09-08
A certificate of analysis is a laboratory's record of what a specific batch of material contained when it was tested. It is not a licence, an approval, or a statement that the material is suitable for anything. It is a measurement, taken on a date, by someone who signed their name to it.
That distinction is the whole reason the document is worth reading. A vendor claiming “99% purity” is describing their marketing. A certificate reporting 99.80% for lot GLP3R60-1001, issued by AMINO METRICS on Aug 10, 2026, is describing a batch — and can be checked: read that certificate.
Six sections, in the order they appear.
Certificates vary in layout between laboratories, but the same six things are on all of them. If one is missing, that absence is itself information.
| Section | What it holds | Why it matters |
|---|---|---|
| Header | Compound name, lot number, vial size | The join between the document and the vial. If the lot number here does not match the vial in front of you, the rest of the page describes something else. |
| Dates | Received, tested, issued | Testing describes the material on the date the sample was drawn. A recent issue date on an old test date tells you when the paperwork was produced, not when the material was measured. |
| Laboratory | Name, address, contact | Who performed the analysis. A certificate issued by the seller is an assertion about itself; a certificate issued by a laboratory that does not answer to the seller is a measurement. |
| Assay rows | Method, specification, result | One row per test. Each should name the method used, the range the result was measured against, and the value found. A result with no method beside it cannot be compared with anything. |
| Conclusion | Pass, fail, or the lab's own wording | The laboratory's summary judgement. Read it against the assay rows rather than instead of them — the rows are the evidence, the conclusion is an opinion about the rows. |
| Sign-off | Analyst or authorised signatory | The person who released the report. An unsigned certificate has no one standing behind it. |
Four checks, in order.
Most of what goes wrong is caught by the first two, and neither requires any chemistry.
Does the lot number match the vial?
Read the lot from the vial label, not from the listing. This is the single check that determines whether the document in front of you describes your material at all, and it is the one most often skipped.
Who issued it, and can you reach them?
Find the laboratory's name. Then establish that it exists independently of the seller — a search, a phone number, a verification link on the lab's own domain. A certificate whose issuer only exists inside the seller's website is a letterhead.
Read the assay rows, not the headline.
The front-page percentage is one row from a panel. Identity confirms the material is the compound named; purity reports how much of the sample is that compound; net peptide content reports how much peptide is actually in the vial. A high purity figure on a vial that is underfilled is still an underfilled vial.
Check the dates against each other.
A test date long before the issue date is not automatically a problem, but it is worth noticing. What the certificate cannot tell you is anything about how the material was handled after the sample was drawn.
What a certificate does not tell you
It describes a sample drawn from a batch on one day. It does not describe the vial you received, except by inference from the batch it belonged to. It says nothing about storage or handling after testing, nothing about whether the material is appropriate for any particular use, and nothing about safety. A document that claimed otherwise would be exceeding what the measurement supports.
Common questions
What should I check first on a certificate of analysis?
The lot number. Everything else on the document describes one specific batch, so if it does not match the vial you are holding, nothing below it applies to your material — however good the numbers look.
Can a certificate of analysis be faked?
A PDF can be edited by anyone. That is why the useful checks are external: whether the laboratory is named, whether it can be contacted independently of the seller, and whether the seller publishes the document rather than describing it. Several laboratories also host verification links that resolve on their own systems.
Should every product have its own certificate?
Every lot should. A certificate describes a batch, not a product line, so a vendor publishing one document for a compound they have sold for years is showing you a batch you almost certainly did not receive.
For laboratory and research use only · Not for human or veterinary consumption · Not evaluated by the FDA