How to Read a Certificate of Analysis (CoA)

A Certificate of Analysis, usually shortened to CoA, is a laboratory document showing the results of tests carried out on a particular batch of a product. For research peptides, it can provide useful information about identity, purity and the sample tested.

At first glance, a CoA can look quite technical. Once you know which parts matter, though, it becomes much easier to understand.

Start with the Sample and Batch Details

Before looking at percentages or graphs, check what was actually tested.

A CoA should clearly identify the sample. Depending on the laboratory and testing process, the CoA may include the peptide name, sample or batch reference, testing date and report number.

These details are important because a laboratory result only relates to the sample submitted for analysis. A purity result has little value if you cannot establish which batch it belongs to.

Check the Purity Result

Purity is commonly assessed using High-Performance Liquid Chromatography (HPLC).

The chromatogram may show several peaks. The main peak normally represents the principal component detected in the sample, while smaller peaks can indicate other components or impurities.

A reported purity figure, such as 98% or 99%, should therefore be read alongside the testing method rather than treated as a standalone quality claim.

Look at Identity Testing

Purity and identity are not the same thing.

A sample can produce a high HPLC purity result, but researchers may still want evidence that the material is the peptide it is claimed to be.

Techniques such as mass spectrometry (MS or LC-MS) can be used to examine molecular mass and support identification of the tested material.

This is why it is useful to check both the purity result and the identity-related data when they are provided.

Check Who Performed the Analysis

Look for the name of the independent laboratory, report or test reference, analysis date and any available verification information.

These details make it easier to assess where the results came from rather than relying on a purity percentage displayed on a product page.

Match the CoA to the Product

Finally, compare the CoA with the batch information supplied with the product. Where batch-specific documentation is available, the references should correspond.

At PeptidesOnline, we provide laboratory documentation so researchers can review available analytical information rather than simply taking a stated purity figure at face value.

A CoA does not tell you everything about a peptide, but knowing how to read one makes it much easier to understand what was tested, how it was analysed and what the reported results actually mean.