A Certificate of Analysis (COA) is the single most useful document when sourcing research peptides. This guide explains what a COA contains, how to verify it, and the red flags that separate a real testing record from a decorative one.
What a COA is
A COA is a lab document reporting the results of testing on a specific batch of material. For peptides, a good COA reports both purity (how much of the vial is the target peptide) and identity (confirmation that the molecule is the one named).
What to look for on a peptide COA
- Purity by HPLC — usually a percentage and a chromatogram (the trace with a main peak). See our HPLC testing guide.
- Identity by mass spectrometry — confirms molecular weight matches the expected value.
- Batch / lot number — must match the number printed on your vial.
- Net peptide content and counter-ion — tells you how much actual peptide is present.
- Testing lab and date — ideally an independent third-party lab.
How to verify a COA against your vial
Match the batch number on the COA to the batch number on the vial label. If they don’t match — or if the same generic certificate is reused for every product — the document tells you nothing about what you actually received. On our lab testing page, COAs are tied to specific batches.
Red flags
- No COA available, or one generic certificate reused across products.
- Purity reported without any identity test.
- A purity claim (“99%+”) with no chromatogram to back it.
- No batch number, lab name, or test date.
See real, batch-matched COAs
Every batch we ship is independently tested and documented. View our testing and COAs.
Frequently asked questions
What’s the difference between purity and identity?
Purity (HPLC) tells you how much of the vial is the target peptide; identity (mass spec) confirms it is the correct molecule. A complete COA reports both.
Why does the batch number matter?
A COA only tells you about the batch it was run on. Matching the batch number on the COA to your vial confirms the document describes your material.
What is ‘net peptide content’?
It’s the amount of actual peptide in the vial after accounting for water and counter-ion. It helps you compare products accurately.
This guide is general educational information about laboratory documentation, not medical or legal advice.