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How to read a peptide COA
Six things to check on any certificate of analysis, what HPLC and mass spec each prove, and the signs a certificate has been recycled from someone else’s batch. Written for people who want to know exactly what they’re looking at.
The six marks on the plate
Lot number
Must match the label on the vial, character for character. A certificate with no lot number describes nothing you own.
Dates
Tested after it was made, and recently enough to describe this batch, not one from years ago.
The lab
Named, with an address, and not the seller. Accreditation (ISO/IEC 17025) is a good sign.
Purity and method
A percentage from HPLC, with the method stated. A main peak share, not a vague “passes”.
Identity
Mass found beside mass expected. They should agree within about one dalton.
The trace
A real chromatogram has a baseline, small peaks and axis labels. A perfect single spike is a warning.
Why it matters
A certificate is the only evidence you have of what is in a vial. Most people glance at the percentage and stop. The guide shows you how to read the rest of the page in under two minutes.