How to Read a Peptide Certificate of Analysis

A peptide certificate of analysis, or COA, is useful only when you can connect its results to the material you are evaluating. Start with the sample and batch details before focusing on the reported percentage.

Match the document to the material

Compare the product name, stated form, and batch or lot identifier with the label and order record. If one document covers several samples, identify the relevant entry. Record any mismatch rather than assuming a similar name refers to the same material.

Identify the question each test addresses

Peptide suppliers commonly use analytical HPLC to evaluate purity and mass spectrometry to support identification. Other measurements may address content or concentration. These results answer different questions, so avoid combining them into one general quality claim.

Read the actual result

Look for a measured value, units where relevant, a method reference, and any stated acceptance criterion. Distinguish a product specification from a result reported for the submitted sample. A target printed on a specification sheet is not itself evidence that a particular sample was measured.

Keep a short review record

A useful internal note can contain the report identifier, lot number, test date, tests included, documents reviewed, and questions still open. Save the original report so later readers can see the same evidence you used.

Ask focused follow-up questions

If the report does not explain a result, ask which method was used and what the result is intended to establish. Request clarification from the issuer through an independently verified contact route when authenticity is uncertain.

Treat the COA as a defined piece of analytical evidence. Its value comes from a clear connection between the sample, the tests, and the reported findings, rather than from the presence of a certificate alone.

Thermo Fisher Custom peptide synthesis brochure: https://documents.thermofisher.com/TFS-Assets/LSG/brochures/custom-peptide-synthesis-brochure.pdf

GenScript Recommended Peptide Purity Guidelines: https://www.genscript.com/recommended_peptide_purity.html