How to verify peptide quality, and spot a bad certificate
Quality on a research peptide is not a claim, it is a document. A batch that has been tested carries a certificate of analysis, and the certificate is checkable. Here is how to read one and what a weak supplier gets wrong.
The two checks that matter
A tested batch stands on two independent results: purity by RP-HPLC (held here to not less than 98.0 percent of the peak area, any single related substance under 1.0 percent) and identity by ESI mass spectrometry (the measured mass matches the labelled peptide). Purity without an identity check is half a result. What each field means, field by field, and the quality page sets out how a batch is released.
Match the certificate to the vial
A certificate is for one batch. Its batch number should match the number printed on the vial label, the carton and the packing list. If the number on the paper does not match the number on the glass, the certificate is not for what you are holding.
What a weak supplier gets wrong
- No certificate, or one certificate reused across every batch (a real COA is per lot).
- A purity figure with no chromatogram and no mass-spec identity behind it.
- A batch number on the paper that does not match the number on the vial.
- A round "99 percent" with no method, no wavelength, no date and no lab named.
- Purity quoted but water, related substances and content left off, so the one number stands alone.
Verify a batch here
Enter the batch number in the COA lookup to pull the certificate on file, no sign-in. What each field on the certificate means.
Vetting a supplier more broadly? How to choose a wholesale peptide supplier.