How to Read a Peptide Certificate of Analysis (COA)
By Lemon Labs Research Desk · Updated June 29, 2026
In short
A Certificate of Analysis (COA) is the document that proves a peptide is what the label says. The two analyses that matter most are HPLC (which reports purity as a percentage, ideally ≥99%) and mass spectrometry (which confirms identity by molecular weight). A trustworthy COA is lot-specific and issued by an independent laboratory.
Why the COA is the most important document
Research is only as reliable as the material behind it. A COA is the analytical record that lets you verify a peptide’s purity and identity before you use it. Without one — or with a generic, non-lot-specific one — you cannot confirm what is actually in the vial.
HPLC: the purity number
High-Performance Liquid Chromatography (HPLC) separates the components of a sample and reports the target peptide as a percentage of the total. This is the purity figure, and research-grade material should read ≥99%. The COA should show the chromatogram or at least the integrated purity value, not just a headline claim.
Mass spectrometry: the identity check
Mass spectrometry (MS) measures the molecular weight of the peptide and confirms it matches the expected mass for that sequence. HPLC tells you how pure the material is; MS tells you it is the right molecule. A complete COA includes both.
Lot number, date, and independence
A credible COA is tied to a specific lot or batch number and a test date, and is issued by an analytical laboratory with no financial stake in the result. If a certificate is not lot-specific, it does not describe the material you actually received. Browse a supplier’s published COA library to confirm this practice is routine, not promised.
Research-use-only statement
This compound is supplied strictly for in-vitro research and laboratory use. It is not a drug, supplement, food, or cosmetic, has not been evaluated by the FDA, and is not intended to diagnose, treat, cure, or prevent any disease. It is not for human or veterinary use. All information here summarizes published scientific literature for educational purposes for qualified researchers — it is not medical advice and does not describe human administration.
Reference compounds mentioned
Frequently asked
What two tests matter most on a peptide COA?
HPLC, which reports purity as a percentage (ideally ≥99%), and mass spectrometry, which confirms the peptide’s identity by molecular weight. A complete COA includes both.
What does ≥99% purity mean?
It means HPLC analysis found the target peptide to make up at least 99% of the sample, with impurities below 1%. This is the standard for research-grade reference material.
Why does the lot number matter?
A COA is only meaningful if it is tied to the specific lot you received. A lot-specific certificate proves the analysis describes your actual material, not a different batch.