Quality
How to Read a Certificate of Analysis (COA)
What each field on a COA actually tells you, and what to check first.
PeptiLab editorial team · Research desk · 28 April 2026 · 1 min read
Key takeaways
- A COA should show a batch code, test date, purity percentage and test method.
- HPLC (High-Performance Liquid Chromatography) is the standard method for purity testing.
- Cross-check the batch code on the COA against the code printed on the vial.
A certificate of analysis (COA) is a third-party lab report confirming what a peptide vial actually contains. Here's what to look for.
The fields that matter
- Batch code. This should match the code printed on the vial itself. If it doesn't, the COA isn't for that specific batch.
- Test date. Testing should have been performed reasonably close to the production date, not years earlier.
- Purity percentage. Reported as a percentage from HPLC analysis. Research-grade peptides are typically tested above 98% purity.
- Test method. HPLC (High-Performance Liquid Chromatography) is the standard method; mass spectrometry is sometimes included alongside it to confirm molecular identity.
Cross-checking a COA
The single most useful check is matching the batch code on the document to the code printed on the vial label. A COA for the wrong batch, even a genuine one, tells you nothing about the vial in front of you.
Research-use-only
This guide explains how to read a standard lab document. It is not medical advice.
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For research use only. Not for human consumption, medical treatment, or veterinary use. Full disclaimer