Does a COA mean a peptide is safe?

No. A Certificate of Analysis reports what a laboratory measured in one sample, such as identity, purity or quantity. It does not establish that a product is safe, sterile (unless sterility was tested), legal or suitable for any use.

Is a COA from the vendor as good as one from an independent laboratory?

They are different kinds of evidence. A report issued by an independent laboratory, with a route to confirm it with that laboratory, is stronger than a document the seller produced itself. Either can be wrong, so check how the report can be verified.

What is the most important thing to check first?

That the batch or lot number on the report matches the one on your vial, and that the report can be confirmed with the issuing laboratory (a verification key, QR code or lookup). Without those two things the document describes some sample, not necessarily yours.

How to read a peptide Certificate of Analysis

By PeptideProof · Updated 12 October 2026 · 8 min read

A Certificate of Analysis (COA) is a document that reports the results of tests on a sample. It is the main piece of evidence behind a research peptide, and it is easy to read wrongly. This guide walks through what each part means, what a COA can and cannot tell you, and a checklist to run through before you rely on one.

What a COA is — and what it isn’t

It describes a sample. The results apply to the material the laboratory received, labelled with a batch or lot number. They apply to your vial only if your vial really came from that batch.
There is no single format. Laboratories lay reports out differently, and some documents called COAs are produced by the seller rather than by an independent laboratory.
It is a snapshot. It shows results on a date, with named methods. It says nothing about how the material was stored afterwards.

The parts of a typical report

1. Who issued it

The laboratory name or letterhead, and, more usefully, a way to confirm the report with that laboratory: a report or task number, a verification key, a QR code, or an online lookup. A letterhead on its own is easy to copy.

2. Report number and sample details

A unique report (or task) number, the sample name, the batch or lot number, the declared quantity, and who ordered the test. The batch number is what ties the report to a product.

3. Dates

Usually the date the sample was received, the date it was analysed and the date the report was issued. They should run in that order. A report issued before the sample arrived is a reason to look closer.

4. Methods

Named techniques such as HPLC with UV detection (purity and content) and LC-MS or mass spectrometry (identity). A result without a stated method is much harder to interpret.

5. Results

The core results for a peptide are usually these three, and they answer different questions:

Identity — is it the right molecule? Mass spectrometry measures molecular mass. For peptides, the report often lists a charge state such as [M+4H]4+ with the measured value.
Purity — of the material that was detected, how much is the main peptide? Usually reported as a percentage from an HPLC chromatogram.
Quantity (content) — how much peptide is actually there, compared with what the label says.

Many people read “99% purity” as “99% of the vial is the peptide”. It does not mean that — see how the three numbers differ.

Some reports add endotoxin, sterility, heavy-metal or residual-solvent results. Where those are missing or marked “not tested”, that is an absence of evidence, not a pass — here is what each test measures.

What a COA can’t tell you

Whether a product is safe, legal or suitable for any use.
That the vial in your hand is the material that was tested.
Anything about a property that was not tested.
That the document itself is genuine — that needs a check with the laboratory.

A short checklist

Does the batch number match your vial and the vendor’s listing?
Can the report be confirmed with the laboratory (key, QR code, lookup)? Did you do it?
Are the dates in a sensible order?
Are the methods named, and is identity shown by mass spectrometry?
Is the quantity found close to the quantity declared?
Which tests are missing or “not tested”?
Does anything look copied from another report? Ten things to check.

You can see this checklist applied to a sample document in the example report, and PeptideProof runs it on your own COA in about a minute.

Frequently asked questions

Does a COA mean a peptide is safe?: No. A Certificate of Analysis reports what a laboratory measured in one sample, such as identity, purity or quantity. It does not establish that a product is safe, sterile (unless sterility was tested), legal or suitable for any use.
Is a COA from the vendor as good as one from an independent laboratory?: They are different kinds of evidence. A report issued by an independent laboratory, with a route to confirm it with that laboratory, is stronger than a document the seller produced itself. Either can be wrong, so check how the report can be verified.
What is the most important thing to check first?: That the batch or lot number on the report matches the one on your vial, and that the report can be confirmed with the issuing laboratory (a verification key, QR code or lookup). Without those two things the document describes some sample, not necessarily yours.

See it on a real document

PeptideProof reads a COA for you and shows what is only reported, what has no evidence and what looks inconsistent. See an example first, or check your own — new accounts include free analyses.

See an example report Verify a COA

More guides

Educational information about reading laboratory documents. It is not medical, dosing or purchasing advice, and it doesn’t say that any product is safe, legal or suitable for any use. See the medical and research-use disclaimer.