COA Library: What Is a Certificate of Analysis?

What Is a COA?

A COA (also written CoA) is a Certificate of Analysis. It is a report from a laboratory that shows what was found when a specific batch of a product was tested. For research peptides, it is the document that backs up what is written on the label.

What Does a COA Mean?

A COA tells you three things about one specific lot: what the material is, how pure it is, and who tested it. A peptide vial is just a white powder, so you cannot judge it by looking at it. The COA is the evidence.

What Is on a Good COA?

• Laboratory name: an independent, identifiable lab.
• Lot (batch) number: it must match the lot on the vial you hold.
• Test date: recent, ideally within the last 12 months.
• HPLC purity: the percentage of the sample that is the target peptide, with the chromatogram attached.
• Mass spectrometry (MS): the measured molecular weight compared with the expected weight, which confirms identity.
• Appearance and content: for example, a white freeze-dried powder and the amount of peptide per vial.

HPLC and MS in Plain English

HPLC (high-performance liquid chromatography) separates a sample into its parts. One tall peak means a clean sample, and purity is that peak's share of the total. MS (mass spectrometry) weighs the molecules to confirm the right peptide is in the vial. You need both: a pure sample of the wrong peptide still passes HPLC.

Why Lot-Matched and Third-Party Matter

A COA only counts if it was issued for the same lot as your vial and was produced by a lab that does not sell the product. A generic or copied COA proves nothing about your batch.

Red Flags

• No lot number, or a lot number that does not match the vial.
• No lab name, address or contact details.
• A purity figure with no chromatogram.
• The same COA used for every product or every lot.
• Edited, cropped or low-quality screenshots.

For a deeper guide, read Peptide Lab Testing & COAs Explained, or use our supplier checklist.