How to Read a Peptide COA (Certificate of Analysis)
A COA is the lab report that tells you what’s actually in a vial — how pure it is and whether it’s the right molecule. Here’s how to read one, what the numbers mean, and how to tell a real one from a decorative PDF.
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What is a COA?
A Certificate of Analysis is a document from an analytical lab reporting the results of testing a specific batch of a peptide. At minimum it identifies the compound, states its measured purity, and confirms its identity — usually with two techniques: HPLC for purity and mass spectrometry for identity.
Why it matters
Peptides are sold as research chemicals with little oversight, so the COA is often the only objective evidence of what you have. It answers two questions: is this the right molecule (identity), and how much of the sample is that molecule (purity). Everything downstream — your dose calculation, your expectations — assumes the vial contains what the label says. The COA is what backs that assumption.
HPLC purity — the percentage
HPLC (high-performance liquid chromatography) separates the sample into its components and measures how much of it is the target peptide versus related impurities (truncated or modified sequences). The result is a purity percentage — you’ll typically see something like 98%+. The COA usually includes the chromatogram: a graph with a tall main peak (your peptide) and small side peaks (impurities). A single dominant peak is what you want to see.
Mass spectrometry — the identity check
HPLC tells you the sample is pure; it doesn’t prove it’s the right peptide. That’s what mass spectrometry (MS) is for. MS measures the molecule’s mass and compares it to the expected molecular weight for that peptide. If the measured mass matches the theoretical mass, the identity is confirmed. A complete COA shows both the HPLC purity and the MS identity.
What a legitimate COA includes
- The peptide name and sequence, and its expected molecular weight.
- A batch or lot number that ties the report to a specific production run.
- HPLC purity % with the chromatogram image.
- Mass spec result confirming the molecular weight.
- The testing lab’s name and the test date.
Red flags of a fake or reused COA
- No batch/lot number, or the same COA image used across many different products.
- Purity only, with no mass-spec identity confirmation (or vice versa).
- No named lab, or a lab that can’t be contacted to verify the report.
- A molecular weight on the report that doesn’t match the peptide’s known weight.
- Blurry, cropped, or edited-looking chromatograms.
COA FAQ
What does “98% purity” on a COA mean?
It means the HPLC analysis found the target peptide made up ~98% of the peptide content in the sample, with the rest being related impurities (truncated or modified sequences). For research peptides, purity in the high-90s is generally considered good.
What’s the difference between HPLC and MS on a COA?
HPLC (high-performance liquid chromatography) measures purity — how much of the sample is the intended peptide. Mass spectrometry (MS) confirms identity — that the molecule’s measured mass matches the expected molecular weight of that peptide. A good COA shows both.
Can a COA be faked?
Yes. A PDF is easy to copy, reuse, or edit. Trust is higher when the COA is tied to a specific batch/lot number, comes from a named third-party lab, and can be verified with that lab directly — not just a generic image reused across products.
Does a COA make a peptide safe to use?
No. A COA speaks to identity and purity of the sample tested — not to whether a compound is safe or appropriate for you. It does not replace medical guidance, and many research peptides are not approved for human use.