How to Read a Peptide Certificate of Analysis (CoA)

If you buy research peptides, the Certificate of Analysis is the most important document you'll ever look at — and the one most first-time buyers skip. It's the laboratory report that tells you what is actually in the vial, rather than what the label claims. Here's how to read one properly.

What a CoA is

A Certificate of Analysis (CoA) is a lab report produced when a production lot is tested. A genuine CoA is specific to a batch, produced when a production lot is tested against defined analytical methods, and it states measurable results specific to that batch — not marketing language. If a seller offers only a generic "99% pure" claim with no document behind it, you have no way to verify the material.

The numbers that matter

HPLC purity. High-performance liquid chromatography separates the sample into its components and measures how much of it is the target peptide, expressed as a percentage (for example, 99.2%). Reputable research-grade material is typically 98% or higher. This is the headline figure.

Mass spectrometry (identity). This confirms the molecular weight of the compound matches the intended peptide — proving the vial contains what the label says it does, not a different or substituted compound.

Endotoxin and sterility. Depending on the research application, these results indicate contamination levels and are part of a complete analytical picture.

The details that prove it's real

Batch / lot number. The CoA must reference the exact lot number printed on your vial. A certificate that doesn't match your lot number tells you nothing about the material you actually received.

Testing methods. The result is only as meaningful as the methods behind it. HPLC purity and mass-spectrometry identity are the checks that matter — and a CoA that names its methods and matches your exact lot number is what makes the numbers verifiable.

Date. A manufacture and test date lets you place the material in time.

How to verify before you buy

The best sellers let you check a batch before you order. At DNR Peptides, every lot links to its own Certificate of Analysis, and you can enter any batch code into our on-site verification tool to see the purity, identity, sterility and testing lab on file for that specific lot.

The bottom line

If a supplier cannot produce a batch-specific Certificate of Analysis, treat any purity claim as unverified. In a market where quality varies enormously, the CoA is how you separate reference-grade research material from guesswork.

DNR Peptides supplies research peptides for laboratory and research use only. Products are not for human or veterinary use. This article is educational and not medical advice.