Red flags
The supplier behaviors that should stop your purchase.
If you see any of these, walk away. They're not "warning signs" — they're disqualifying.
A purity claim with no chromatogram
">99% pure" written on a page with no underlying HPLC chromatogram is marketing copy. A real reference supplier publishes the chromatogram, the wavelength, the retention time of the target peak, and the integration that produced the percentage. Without those, the percentage is unverifiable.
The same COA across multiple lots
We've documented this. Two vials with different lot numbers, one identical PDF. If the COA is supposed to be lot-specific and the supplier reuses one across lots, they are not testing each lot — they're producing decorative documents.
Stock-photo chromatograms
Sometimes the chromatogram on the COA is genuinely from a reference run. Sometimes it's the same generic image found on dozens of supplier sites. Reverse-image-search any chromatogram you're skeptical of. If it appears on multiple unrelated supplier sites, the supplier is decorating, not documenting.
COA available 'on request'
A supplier that publishes COAs only by email request is, at minimum, behind industry practice. At worst, they are buying time to produce a generic COA after the order. Reference-grade suppliers publish per-lot COAs on the product page.
No batch number on the vial label
Without a lot number on the physical vial, you cannot match the COA to the material. The lot number is the audit trail. Vials with no lot number are a sign the supplier doesn't track lots — which means they cannot meaningfully test them either.
No published refund policy
Suppliers without a written refund policy on the site will, in our experience, dispute every refund request individually. A clear written policy is table stakes for any reference-grade vendor.
Live-chat or phone with no technical knowledge
Try asking the support agent "what's the counter-ion on lot XYZ?" or "what's the endotoxin figure?" — if the answer is escalation or a generic deflection, the supplier doesn't internalize the technical content. That's a procurement problem.
Mass-spec data not on the COA
Mass spectrometry is cheap. Every reference-grade lot should have a mass-spec confirmation matching theoretical molecular weight. A COA without it indicates either the supplier doesn't run mass-spec or doesn't share it — neither is acceptable.
Cosmetic-grade claims dressed as research-grade
Some suppliers slap "research grade" on cosmetic-grade material. The tell: no endotoxin testing, no bioburden, and pricing significantly below research-supplier norms. For chemistry-only research, cosmetic-grade can be fine. Just know what you're buying.
The website looks like dropshipping
Generic Shopify theme, stock peptide imagery, supplier name that doesn't match the contact email domain, no "about" page beyond a paragraph of vague language. The look isn't proof of fraud, but it correlates strongly with poor documentation practices.
When in doubt
Order a small reference quantity first. Verify the COA against the lot. If anything doesn't line up, walk before scaling the order. The cost of a small verification order is much lower than the cost of building research on a bad supplier.