How to Read a Peptide Certificate of Analysis (COA)
Research & educational use only. This content is not medical advice. Consult a qualified healthcare professional before using any peptide compound.
A certificate of analysis (COA) is a laboratory document that reports what a specific peptide batch actually contains — its identity, its purity, and sometimes its safety testing. Learning to read one is the single most useful skill for evaluating a research-chemical vendor, because it turns marketing claims into verifiable data.
What is a certificate of analysis?
A COA is issued by a testing laboratory (ideally independent of the vendor) for a particular batch or lot of material. It states which analytical methods were run, the results, and whether the batch passed the lab’s acceptance criteria. A COA is batch-specific: a clean COA for one lot says nothing about a different lot, which is why batch IDs and dates matter.
Which tests should a COA include?
- Identity / purity by HPLC or LC-MS. High-performance liquid chromatography (HPLC) and liquid chromatography–mass spectrometry (LC-MS) confirm the peptide is what the label says and measure how much of the sample is the target compound (reported as a purity percentage).
- Mass confirmation (MS). Mass spectrometry confirms the molecular weight matches the expected sequence.
- Endotoxin and sterility. For anything intended for injection in a research context, endotoxin (LAL) and sterility testing matter for contamination, not just purity.
On PeptidesHub, vendor lab results are tagged by test type (HPLC, LC-MS, NMR, endotoxin, sterility) so you can see which methods a vendor actually publishes.
What purity percentage is meaningful?
Purity is usually reported as a percentage of the chromatogram area attributable to the target peptide. Higher is better, but the number is only meaningful alongside the method (HPLC area-percent is the common standard) and the batch it describes. A purity figure with no method, no batch ID, and no lab name is marketing, not data.
What are the COA red flags?
- No lab name, or a lab that cannot be independently identified.
- No batch or lot number tying the COA to the product you’d receive.
- An image of a COA with no verifiable source, or one reused across many products.
- Purity claims with no chromatogram or method listed.
- Third-party testing claimed but never actually shown.
When a COA can’t be tied to a specific batch from an identifiable lab, treat it as absent.
How does PeptidesHub use COAs?
Community-submitted lab results feed a vendor’s transparency and quality scores after moderator review. Third-party tests (HPLC, LC-MS, NMR) are weighted more heavily than vendor self-reports. You can submit a COA on any vendor page, and browse approved results in the vendor’s lab-testing section.