How to Read a Peptide Certificate of Analysis (COA)

Most peptide vendors say “third-party tested.” Far fewer name the lab. Fewer still publish the actual test so you can read it before you buy. If you work with research peptides, the Certificate of Analysis is the one document that tells you what is really in the vial. Here is how to read one, at any vendor, anywhere.

For laboratory research purposes only. Not for human consumption.

What a Certificate of Analysis is

A Certificate of Analysis (COA) is the laboratory report for a specific research material. It records what was tested, how it was tested, and the results, issued by a laboratory rather than by the seller’s marketing team. A real COA turns “trust us” into “read it yourself.”

For research-grade peptides, a credible COA answers two separate questions:

• Identity: is this actually the compound on the label?
• Purity: how much of the sample is that compound, and what else is in it?

A label and a price tell you neither. The COA does.

The five things a real peptide COA should show

1. A named laboratory. Not “an independent lab.” A specific, third-party laboratory you can look up. An anonymous lab is not verification.
2. HPLC for purity. High-Performance Liquid Chromatography separates the sample and measures how much is the target compound versus impurities. This produces the purity figure.
3. Mass spectrometry (MS) for identity. MS confirms the molecular weight, which confirms the compound is what the label claims. Purity without identity is half a test.
4. The actual values, against a stated specification. A credible report shows the measured purity and the specification it is held to, for example a specification of ≥98% with a typical result near 99%. Numbers, not adjectives.
5. A date, tied to the material it certifies. A COA should be current and connected to the material you are buying, not a years-old generic sheet reused across everything.

Miss any of these and you are reading a brochure, not a test.

HPLC vs. mass spec: purity is not identity

These two get conflated, so it is worth separating them.

• HPLC answers “how pure?” It tells you what fraction of the sample is the intended compound. A high HPLC number alone does not prove the sample is the right molecule, only that it is mostly one thing.
• Mass spectrometry answers “is it the right molecule?” It confirms identity by molecular weight.

You want both, on the same COA. HPLC purity plus MS identity is the standard. One without the other leaves a real question open.

What the purity number actually means, and why “100%” is a red flag

Purity is a measurement, and measurements have limits. A serious supplier states a purity specification, for example ≥98%, and reports the typical result, often around 99%, by HPLC and MS.

Be cautious with “100% pure” or “100% purity” claims. No analytical method reports a true 100 percent, so a badge that says so is telling you the figure came from marketing, not from a lab. A precise, slightly-less-than-perfect number with a method behind it is more trustworthy than a round, unverifiable one.

Red flags when reading a peptide COA

• No named lab, or “tested by an independent third party” with no name.
• Purity but no identity (HPLC with no MS), or the reverse.
• An undated COA, or one with no link to the specific material.
• A “100% purity” claim, or any absolute with no method shown.
• An image of a COA with no source you can verify. A screenshot is not a published test.

The 30-second COA checklist

Use this for any vendor, including this one:

• The laboratory is named.
• HPLC purity is reported.
• Mass spec identity is reported.
• There is a purity specification and a measured value, not just “high purity.”
• The COA is dated and tied to the material.
• The figure is realistic (a specification such as ≥98%, not “100%”).

If all six are true, you can verify what you are buying. If not, ask the vendor for the document, and notice whether they can produce it.

Where GREYGEM’s COAs live

We built GREYGEM around this exact test. Every compound is independently tested, with its Certificate of Analysis published so you can read identity and purity before you order, not after. The laboratory we use is named on our compliance page.

• Read the tests: COA Library
• See the methodology and the named lab: Compliance
• Browse the catalogue: Shop

Don’t take our word for it. Read the documentation.

Frequently asked questions

What should a peptide COA include?
A named third-party laboratory, HPLC purity, mass-spectrometry identity, the measured values against a stated specification, and a date tied to the material tested.

What is the difference between HPLC and mass spectrometry on a COA?
HPLC measures purity, how much of the sample is the target compound. Mass spectrometry confirms identity, that the compound is the right molecule. A complete COA shows both.

Is 100% peptide purity possible?
No analytical method reports a true 100 percent. A credible supplier states a specification such as ≥98% with a typical result near 99%. Treat “100% purity” claims as a red flag.

How do I know a COA is real and not a stock image?
It should be published and traceable to a named lab and the specific material, current and dated, not an undated screenshot reused across products.

GREYGEM supplies research-grade peptides for laboratory research only. For laboratory research purposes only. Not for human consumption. This article is educational and does not describe or recommend human or veterinary use.