Identity — mass spectrometry
The COA should report a measured molecular mass within a small tolerance (typically ≤ 0.1 Da of theoretical) confirming the sample is the intended peptide. This is the identity check; without it, a high purity number is meaningless because you do not know what was purified.
Purity — HPLC
The HPLC section reports the percentage of the sample that is the target compound, usually as area-under-curve. A reference-standard-grade research peptide is ≥99%. Look for the chromatogram, not just a stated number.
Net peptide content
Lyophilized peptide vials contain the peptide plus residual water and counter-ions. Net content tells you how much actual peptide is present — important for accurate experimental work.
Water content (Karl Fischer)
High residual water accelerates degradation. Karl Fischer titration quantifies it; lower is better for stability.
Endotoxin and sterility (where tested)
Few research suppliers test endotoxin and sterility, but these panels indicate a higher level of quality control. Their presence on a COA is a differentiator.
Verification — is the COA real?
The best COAs are independently issued and carry a verification key or QR code that resolves on the testing laboratory's own site. A COA you cannot independently verify on the lab's domain should be treated with caution.
See it in practice
Every Ethos Bio compound ships with an independent, mass-spec-verified Certificate of Analysis. Browse the public COA library.
Frequently asked questions
What does a peptide COA show?
A complete peptide COA shows mass-spectrometry identity confirmation, HPLC purity percentage with a chromatogram, net peptide content, water content (Karl Fischer), and — for higher-grade suppliers — endotoxin and sterility results, plus a verification key.
How do I know a COA is authentic?
Independent COAs carry a unique verification key or QR code that resolves on the testing laboratory's own website. If the result cannot be confirmed on the lab's domain, treat the document with caution.
What is the difference between purity and identity on a COA?
Identity (mass spectrometry) confirms the sample is the intended molecule; purity (HPLC) measures what percentage of the sample is that molecule. Both are required — a purity figure is meaningless without an identity confirmation.