How to read a certificate of analysis
A certificate of analysis says which batch was tested, by whom, how and with what result. Check that all four match the vial in front of you.
Updated 26 October 2026
The short answer
A certificate of analysis (COA) is a laboratory's report on one batch of a compound. A useful one names the laboratory, identifies the batch, states the test date and the methods used, and gives the measured results. Check that the batch on the certificate is the batch on your vial.
1. Who tested it
The laboratory should be named, with an address or website you can check. A certificate with no laboratory name, or one issued only by the seller, tells you less than one from an independent laboratory.
2. Which batch
The certificate should carry a batch or lot number. It applies to that batch only. A certificate for a different batch says nothing direct about yours.
3. When
The test date shows how old the result is. Peptides can degrade over time, especially after a vial is opened or reconstituted, so an old certificate describes the batch as it was then.
4. Purity: HPLC
High-performance liquid chromatography (HPLC) separates a sample into its components. The report shows a chromatogram, a plot with a peak for each component, and purity is the main peak's area as a share of the total area of all peaks. A result of 98% means the main peak accounts for 98% of what the detector measured, under that method. Different methods and detection wavelengths can give different figures for the same material, so the method should be stated.
5. Identity: mass spectrometry
Mass spectrometry (MS) measures the mass of the molecules in the sample. The certificate should give the measured mass next to the expected mass for the compound. A close match supports that the compound is what the label says; purity alone does not show that.
6. Content and other tests
Some certificates also report the net peptide content (how much of the powder is peptide rather than salts and water), the water content, or tests for endotoxin and sterility. These are separate measurements, and a certificate that leaves them out has not tested them.
On this shop
Certificates are shown on each product page as a table with the PDF beside it. See testing and quality for where things stand.