Quality
How to read a peptide certificate of analysis
· 6 min read
A certificate of analysis is the only objective evidence you have about what is actually in a vial. Knowing how to read one — and how to verify it independently — is basic due diligence for any laboratory buying research material.
Identity: mass spectrometry
Mass spectrometry confirms the molecular weight of the material against the theoretical mass of the stated sequence. If the observed mass does not match, the vial does not contain what the label claims, regardless of how clean the purity figure looks.
Check that the sequence and expected mass printed on the report match the compound you ordered, not a related analogue.
Purity: the HPLC chromatogram
Reverse-phase HPLC separates the target peptide from synthesis by-products. Purity is reported as the target peak's share of total peak area — 98% means 2% of detected material is something else.
Look at the trace, not just the number. A single dominant peak with a flat baseline is what you want; a cluster of shoulder peaks suggests incomplete purification even when the headline figure is acceptable.
Lot number and date
- The lot number on the report must match the lot printed on the vial you received.
- A report dated long before your batch was produced is not a batch-matched COA.
- Generic 'sample' reports with no lot reference tell you nothing about your specific material.
Third-party verification
Reports from independent laboratories such as Janoshik Analytical carry a verification key that can be checked directly with the testing lab. That check confirms the report was actually issued and has not been altered.
Any supplier can produce a PDF. A verification key is what makes the document meaningful.
What a COA does not tell you
- Nothing about biological activity or suitability for any particular assay.
- Nothing about endotoxin or sterility unless those tests are explicitly reported.
- Nothing about how the material was stored or transported after testing.
Frequently asked
What purity should research peptides be?
For most laboratory applications, 98% or higher by HPLC is the working expectation, with a batch-matched report to evidence it. Some assay types tolerate less; the report lets you make that call rather than guess.
How do I verify a Janoshik report?
Each report carries a verification key that can be entered on the testing laboratory's own site to confirm the document is genuine. Our COA library publishes the keys alongside each batch so you can check them independently.
Research use only. All material referenced is supplied for in-vitro laboratory research by institutions and registered businesses. Not for human or veterinary use, and not for diagnostic or therapeutic purposes.