Most certificates of analysis for research peptides get a two second look. Here is what each part actually tells you, in the order I check it.

1. Who ran the test

A real certificate names the laboratory, its address, and a report or accession number. "Third-party tested" with no lab name is a claim, not a document. If the lab has a public lookup, search the number there yourself instead of following a link the seller gave you. The lab's copy and the seller's copy should match on compound, lot, date and results.

2. Identity comes first

Mass spectrometry answers a simple question: is the molecule in the vial the molecule on the label? The report should list an expected mass and an observed mass that agree within the instrument's tolerance. A purity number with no identity result tells you the sample is one thing, but not which thing.

3. HPLC purity

HPLC separates the sample and reports each peak as a share of total peak area. A figure like 99.4% means the main peak makes up 99.4% of the detected area at the wavelength used, usually 214 nm for peptides. Things worth noticing:

  • Purity is an area percentage, not a weight percentage.
  • The chromatogram matters as much as the headline number. Look for a clean main peak and small, separated minor peaks.
  • If every lot from one seller reads exactly 99.9%, ask whether each lot was really tested.

4. Net peptide content

This is the line most people skip. A vial labelled 10 mg can hold 10 mg of powder, but part of that powder is counter-ion salt and moisture. Net peptide content reports how many milligrams of actual peptide are in the vial. A result near or above the label means the label is honest. A result far below it means you are comparing prices per vial, not per milligram of peptide.

5. Match the lot to the vial

The lot printed on the vial must be the lot on the certificate. One good certificate reused across many lots or many months is a red flag. Dates should also make sense: a test date before the manufacture date means something is wrong.

6. Quick red flags

  • The lab name does not lead to a real lab with a working website.
  • The report number returns nothing at the lab, or returns a different compound or lot.
  • The file is an image only, with fonts or alignment that look edited.
  • The "verify" link points to the seller's own domain.

A small checklist

  1. Find the lab and the report number.
  2. Look the number up on the lab's own site.
  3. Confirm identity, then purity, then net content.
  4. Match the lot to the physical vial.
  5. Keep a copy with the date you checked it.

I work on lab documentation at Luvaminos, a US supplier of research-use-only materials, and we publish one certificate per lot, so these are the checks we expect people to run on ours as well. If you handle lab reports in your own work and see something I missed, leave a comment and I will add it.