Certificate of Analysis Explained

A Certificate of Analysis is a document that reports the quality testing performed on a specific batch of material. It is informative — but it is also frequently misunderstood, misused, or counterfeited.

Educational research-literacy content only. Not medical advice, not dosing guidance, not sourcing advice, and not a protocol for human or animal use. See our responsible information policy.

What a COA typically reports

• Compound identity (typically HPLC and/or mass spectrometry).
• Purity (typically HPLC area-percent).
• Batch / lot number.
• Date of analysis.
• Sometimes: water content, residual solvents, peptide content vs net weight.

What a COA does not establish

• Sterility — purity is a chemical metric, not a microbial one.
• Endotoxin content — typically not on a standard peptide COA.
• Lot-to-lot consistency — a COA describes one batch.
• Authenticity of the document — see below.
• Safety for human or animal use — that is not what the document is for.

Common COA problems

• COAs photocopied or reused across unrelated batches.
• HPLC traces that have been digitally edited.
• COAs from a third-party lab that has no public registration.
• COAs that report only a single test (e.g. mass spec) without purity.
• COAs that describe a peptide other than the one the vial contains.

Third-party testing

An independent third-party test — performed by a laboratory with no commercial relationship to the supplier — is stronger evidence than an in-house COA. Even then, a third-party test does not address sterility or endotoxin and is performed on a sample, not on the entire batch.

What COAs mean for readers

A COA can help a researcher confirm that they are receiving roughly what was ordered. It does not establish that a product is safe for use. See our explainer on purity vs sterility vs endotoxin.