BEGINNER GUIDE
How to Read a Certificate of Analysis
A CoA is the most important document behind any research peptide — but only if you can read it. Here’s a line-by-line, beginner-friendly walkthrough.
What a CoA actually is
A Certificate of Analysis (CoA) is a batch-specific document from the testing lab that reports what a particular production batch actually contains. It’s the paper trail that turns "trust us" into "here are the measurements".
Crucially, a real CoA is tied to a batch or lot number — it describes the exact vials it was made from, not the product in general. A generic, batch-less "CoA" is a marketing image, not verification.
The identity section
Near the top you’ll find the product name and sequence, and usually a mass spectrometry result. The mass spec reports a measured molecular weight; if it matches the theoretical weight of the claimed sequence, the identity is confirmed — the vial really is the peptide named.
If the measured and theoretical masses don’t line up, that’s a fundamental problem regardless of anything else on the page.
The purity section
This is the part most people look for: the HPLC purity result, expressed as a percentage (you’ll often see figures like ≥98%). It tells you how much of the batch is the target peptide versus impurities. Many CoAs include the actual chromatogram — a graph with a dominant peak — which a legitimate supplier is happy to show.
A high purity figure with a clean single peak is what you want. A vague number with no chromatogram is far weaker.
The housekeeping details
Finally, check the appearance (e.g. white lyophilised powder), the test date and methods, and the batch/lot number that ties it all to your specific product. A complete CoA reads like a short lab report, not a logo.
Every batch we supply has a CoA available on request. If you want the underlying concepts first, see our how to verify peptide quality guide.
KEY TAKEAWAYS
- A CoA is a batch-specific lab report — it must carry a batch/lot number.
- The identity section uses mass spectrometry to confirm the right sequence.
- The purity section reports HPLC percentage; ideally with a clean chromatogram.
- Check appearance, test date, methods and lot number for a complete document.