How we verify / Claims vs COA

Claims vs COA

What each supplier promises (“99% pure”, a 5mg vial) against what its own certificates of analysis actually measured. A 5mg vial measuring 4.6mg or 5.2mg is flagged, and so is a certificate below the purity the website advertises.

How this is checked

• Vial content. Measured net peptide content against the size on the label. Within ±3% is on label, 3–10% is off label, beyond ±10% is a major deviation (under- or overfilled). When a certificate weighs several vials of the batch, the vial farthest from the label is the one judged, and with several purity results the lowest counts. Blends are only checked when the certificate lists each component.
• Purity. HPLC purity on each certificate against the purity the supplier promises site-wide on its own website. Up to 1 point below the claim is amber, more than that is red. Only a direct promise counts (“99%+ purity guaranteed”); explanations of what purity means, one product's figure and page code are not treated as a claim. A certificate that reports only a bound (“>99%”) is judged only when the bound meets the claim, and a specification line is never read as a result.
• Whose certificate. A certificate is only read once our client-identity review has looked at it, and one issued to a different company is left out — whether the automatic check or a manual review found it. A certificate issued to the company that runs the supplier's own website counts as the supplier's. A file hosted on another supplier's website is not counted for this one. The same rules decide which certificates appear on supplier and product pages. Only peptide certificates are read: bacteriostatic water, acetic acid and other diluents are left out, and so are product data sheets, which state a specification rather than a batch result.
• Main impurity. Shown when the certificate itemises it: a named impurity (TFA, deletion sequence, oxidation…) or the largest secondary peak in the HPLC peak table. Most certificates report only a purity figure, so the rest of the sample is not itemised.
• Trust Score. These checks are 10 of the 25 Transparency points: vial content 7 (full credit within ±3%, half up to ±10%, none beyond, over- and underfilled alike), purity 3 (98% is the bar when a supplier advertises no figure). Fewer than 5 readable results gives half credit rather than a guess.
• These are the supplier's own published certificates, read automatically from the PDF or image. Janoshik results tables are read twice from the image, cell by cell, and a figure the two readings disagree on is left out rather than guessed. A certificate covers one batch on one date. We have not tested these batches ourselves.

Built 2026-09-26 from 19019 supplier documents, 9139 of which carried a readable result. Research use only.