How to read a certificate of analysis
Written and maintained by the AVERON Research Desk · Last reviewed September 2026
A certificate of analysis, usually shortened to COA, is a laboratory's written record of what a sample is and what it contains. For research peptides it is the single most useful document you can ask for. It is also easy to misread, and easy to fake when it is only a PDF. This page walks through a typical peptide COA from top to bottom.
Start with who issued it
The first question is not what the numbers say but who produced them. A COA from the seller's own laboratory is a claim. A COA from an independent laboratory, with results you can look up on that laboratory's own system, is evidence. Before reading anything else, find the laboratory's name and the identifiers that let you check the document is genuine.
The identifiers
Task or report number. The laboratory's reference for this specific test. On independent testing platforms it is what you use to look the report up.
Verification key or code. A second identifier that, together with the task number, retrieves the original record from the laboratory's server.
Batch or lot number. The production run the sample came from. This is the most important line on the page for you personally, because a report only describes your vial if the batch number matches the one printed on it.
Sample name. The compound the laboratory was asked to test, as written by whoever submitted the sample.
The results
Identity. Whether the sample is the compound it is claimed to be. Identity is usually confirmed by mass spectrometry, which measures molecular weight and compares it with the known weight of the compound. See mass spectrometry identity testing.
Purity. The proportion of the sample that is the target compound rather than related impurities, measured by HPLC and reported as a percentage. See HPLC purity explained.
Content or amount. How much of the compound the laboratory measured in the vial, which you can compare with the amount on the label. A vial can be very pure and still contain less than the label says, so purity and content are separate questions.
Blends. When a vial contains more than one compound, laboratories generally report the identity and amount of each component. Purity is usually not reported for blends, because the impurities of the different peptides overlap in the analysis and cannot be cleanly separated.
What is usually not on the page
Standard peptide testing does not include sterility, bacterial endotoxin or heavy metals unless those tests were specifically ordered. If they are not listed on the report, assume they were not done. We cover this in what a lab report does not tell you.
A quick checklist
- Is the laboratory independent of the seller?
- Can you look the report up on the laboratory's own system, rather than trusting a file?
- Does the batch number match your vial?
- Does the identity result match the compound on the label?
- Does the measured content match the labelled amount?