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How to Read a Certificate of Analysis
A certificate of analysis (COA) is the document that links a physical vial to the analytical results obtained on it. Read against your protocol, it is the first quality-control gate of a study.
The fields that matter
Batch or lot number. The single most important field. It must match the number printed on the vial you are holding. A certificate for another lot tells you nothing about yours.
Purity (% by HPLC). The proportion of the total peak area attributable to the target peptide. A figure such as ≥ 98.5% is a specification limit as measured on that lot, not a universal guarantee for the product.
Test method. HPLC purity and mass spectrometry answer different questions. HPLC tells you how much of the material is your peptide; mass spectrometry tells you that the dominant peak is the expected molecule. You want both.
Appearance and peptide content. Appearance confirms the material is the expected physical form. Peptide content, where reported, is the mass of actual peptide per vial — it can sit slightly below the nominal fill weight because of residual moisture and counter-ions.
Analyst, method and date. A certificate without a laboratory name and a test date is an unverifiable document.
Checks worth making before accepting a lot
- Vial label batch number equals the certificate batch number.
- Purity meets the limit your protocol specifies, measured by a method your protocol accepts.
- Mass confirms the expected molecular weight within the tolerance stated.
- Certificate date is consistent with the manufacture date on the label.
- The laboratory named is one you can contact if a question arises.
What a certificate does not tell you
A COA is lot-specific analytical data. It is not a statement of suitability for any particular use, and it does not transfer to other batches of the same product. Keep the certificate filed with the batch number, and keep it for as long as your record-retention rules require.
Every P3P-research batch is filed against its lot number and can be retrieved from the Certificate of Analysis lookup using either the product name or the batch number.