How to Read a Peptide COA
A Certificate of Analysis is the only objective evidence of what's actually in a vial — but only if you know what to look for. Here are the five things a genuine COA must show, and the red flags that expose a worthless one.
1. Batch / lot number
The COA must state a batch number, and that number must match the label on the vial you receive. A certificate without a batch number — or one that never changes across months of stock — is not evidence of anything.
2. Testing laboratory and date
A genuine COA names the laboratory that performed the analysis and the date of testing. Recent dates matter: peptide suppliers restock frequently, so a COA from a year ago says nothing about today's batch.
3. HPLC purity result and chromatogram
High-Performance Liquid Chromatography separates the sample into its components. The COA should state the purity percentage (reputable suppliers specify ≥99%) and ideally include the chromatogram itself — the graph showing one dominant peak. Multiple significant peaks indicate impurities.
4. Identity confirmation
Purity alone doesn't prove the vial contains the right compound. Look for identity confirmation — typically mass spectrometry (MS) showing the measured molecular weight matching the compound's theoretical mass.
5. Quantity verification
The stated fill (e.g. 10 mg) should be verified, not assumed. Under-filled vials are one of the most common problems with untested suppliers.
Red flags
- No batch number, or a batch number that doesn't match the vial label
- No named laboratory — "tested in-house" is not independent verification
- A purity figure with no chromatogram or supporting data
- The same certificate reused across every product on the site
- A supplier that only shows the COA after you've paid
Every Peptigen Labs product page publishes the independent COA for the current batch — you can check each one against this list before ordering. See also our UK buyer's checklist or the full FAQ.
All products are supplied strictly for laboratory research use only — not for human consumption.