How to read a Certificate of Analysis in under a minute.

The one document that tells you whether a peptide supplier actually knows what is in the pen they just sold you. Here is how to read it in sixty seconds.

A Certificate of Analysis is the difference between buying research material and buying a brochure. Most buyers either never see one or get a generic PDF that could belong to anyone. Here is how to read a real CoA in sixty seconds, and the four red flags to run from.

The three things to check first

Before you read anything else, look at three numbers. Together they tell you ninety percent of what you need to know.

1. Purity by HPLC

Find the chromatogram. Look for the main peak. Next to it, there should be a percentage. That number is the area under the main peak as a percent of all peaks in the sample. If the main peak is 99.13% of the total area, the peptide is 99.13% pure by HPLC.

A credible supplier shows you ≥97% for a release specification and >98% for a typical lot result. If you cannot find a percentage on the chromatogram, the CoA is not useful.

2. Molecular weight confirmation by mass spectrometry

Find the MS section. It will show a theoretical mass (what the target molecule should weigh) and an observed mass (what the lab actually measured). If those two numbers match within a small tolerance, the peptide you are holding is the one on the label.

A sequence check is often included next to the MS data. You do not need to read it yourself. You just need to see that it is there.

3. The batch and date

A real CoA is tied to a specific batch number, a production date, and an expiry. If you cannot find a batch reference on the CoA you were sent, the CoA is generic, and generic CoAs are marketing.

A worked example

Here is what a healthy CoA line looks like in practice:

Four numbers. Together they tell you the peptide is what the label says it is, and that the specific batch you received hits a purity level you can verify.

The four red flags

You will see all of these in the wild. If you see any of them, ask for a better document or walk.

What to do with the CoA once you have it

Save it. Archive it with the batch number and date. If anything ever goes wrong with a peptide, the CoA is your starting point for resolving it. If your supplier cannot give you one at all, you do not have a supplier. You have a dealer.