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Sourcing Peptides Safely: Reading a Certificate of Analysis
HPLC purity, mass spectrometry identity confirmation, endotoxin testing, and the red flags that indicate a recycled or fabricated COA.
The three tests that matter
HPLC establishes purity — look for ≥98% with a visible chromatogram, not just a printed number.
Mass spectrometry confirms identity by matching observed molecular weight to the theoretical mass.
Endotoxin (LAL) testing matters for anything injected and is the test most often missing.
Red flags
No lab name, no analyst signature, or no test date on the certificate.
The same batch number appearing across multiple products, or a PDF with edited text layers.
Purity claims of 99.9% with no chromatogram attached.
A vendor offering dosing advice or medical claims — a legitimate RUO supplier will not.
Storage after you receive it
Lyophilized powder is stable for years at -20°C and months refrigerated. Reconstituted peptide is generally good for 3–4 weeks at 2–8°C.
Protect from light, avoid freeze-thaw cycles once reconstituted, and discard anything cloudy or with visible particulate.