COA stands for certificate of analysis. It is the document in which a laboratory records what it measured in one specific batch. Without a COA, all you know is what the label says.
What is on a COA?
A complete certificate of analysis contains at least the following:
- Product and batch number. The name of the compound and the number of the production run.
- Date of analysis. The day the measurement was made.
- Purity. Usually determined by HPLC and expressed as a percentage.
- Identity. The molecular mass, measured by mass spectrometry and compared with the calculated value.
- The chromatogram. The graph from the HPLC run, showing the main peak and any impurities.
- The laboratory. Its name, and often the analyst’s signature or initials.
Some certificates also list additional tests, such as peptide content, water content, or an endotoxin test.
How to check a COA in five steps
- Compare the batch number. The number on the certificate must match the number on the vial label. A certificate without a batch number tells you nothing about your material.
- Check the date. An analysis from years ago does not add up for a batch you have just bought.
- Look for the method. The certificate should state how the measurement was made: which column, which wavelength, which gradient.
- Verify the mass. The measured mass should fall within a small margin of the theoretical mass. That value follows from the sequence.
- Study the chromatogram. A single sharp main peak and a flat baseline are consistent with high purity. If the certificate gives only a number and no graph, ask for the raw data.
What a COA does not tell you
A certificate describes the batch at the moment it was measured. It says nothing about what happened to the vial afterward. If a product has been stored somewhere warm or humid, its composition may have changed.
A COA also covers only what is on it. If no sterility or endotoxin test is listed, do not assume one was done. And a purity of 99% is not the same as 99% peptide in the powder; we explain the difference in What does 99% purity mean?
Batch-specific or generic
Some suppliers show one certificate per product, regardless of the batch. That is an example certificate. It shows what the supplier once had tested, not what is in current stock. So always ask for the certificate of the batch you receive.
At PulseChem, every vial carries its batch number. The matching certificate is on the product page and on the Lab results page, where you can search by batch number.
How to read the mass spectrum on a certificate is explained in How to read a mass spectrum.
This article is background information on laboratory research. It is not medical advice or instructions for use. All products are for research use only.