How to Read a Peptide Certificate of Analysis
A certificate of analysis documents what is in a vial. This neutral guide explains peptide COA fields and how identity and purity are established.
Identity vs. purity
Identity answers “is this the compound it claims to be?” — typically confirmed by mass spectrometry (the measured mass matches the theoretical mass of the sequence). Purity answers “how much of the sample is that compound?” — typically measured by reverse-phase HPLC and reported as a percentage of total peak area.
The fields you will see
| Compound / sequence | the peptide identity and amino-acid sequence |
| Molecular formula / MW | theoretical formula and mass used for confirmation |
| HPLC purity | % of total area, method noted (e.g. RP-HPLC @ 220 nm) |
| Identity (MS) | observed mass vs. theoretical mass |
| Lot number | ties the document to a specific batch |
| Test date | when the analysis was performed |
Why lot-specific matters
A generic COA describes an idealized product; a lot-specific COA describes the exact batch in your hand. Reference-grade sourcing means the document you read matches the vial you received — same lot number, same analytical run.
Verify before you rely on it
White Label Labs certificates are published per lot as batches are released. Enter a lot number on the verification page to pull the analytical record for that batch.