A certificate of analysis (CoA) is the piece of paper that tells you what is genuinely sitting in a vial of research peptide. The ones worth trusting are batch-specific, meaning they belong to the exact lot that landed on your bench rather than a one-size-fits-all sales sheet. This guide takes you field by field, shows you what a solid CoA looks like, and flags the tell-tale signs of a weak or generic one. It is for qualified researchers, and all material is for in-vitro research only.
The fields a good CoA includes
- The product name, plus its batch or lot number: these need to match the label on your vial. If they do not, the document is not describing your material.
- Identity, confirmed by mass spectrometry: the measured mass shown next to the expected mass from the sequence. A match tells you the molecule is right, and it is both the most important check and the one that goes missing most often.
- Purity (HPLC): a percentage such as ≥99%, plus the chromatogram. Anyone can type a number, so the trace is what actually backs it up.
- Net peptide content: the share of the powder that is really peptide. Since synthetic peptides carry water and counter-ions, a "5 mg" vial hardly ever holds 5 mg of pure peptide. It comes from amino-acid or nitrogen analysis.
- Water content: usually measured by Karl Fischer titration.
- Counter-ion: the acetate or trifluoroacetate (TFA) salt content, read off by ion chromatography or HPLC.
- Appearance, and the date of testing: for example a white freeze-dried powder, together with when it was checked.
What a trustworthy CoA looks like
A good one puts both identity and purity on the page along with the evidence behind them, the MS spectrum and the HPLC chromatogram. It carries the same batch number that is on your vial, and it states the net peptide content so you know the real amount you are working with. If you want to see how those tests actually run, our reference on research peptide purity & testing covers it.
Things that should make you pause
- A batch number that is missing, or does not match your vial: then the document is not about your material.
- A purity percentage with no chromatogram beside it: that is a claim you cannot check.
- Nothing from mass spectrometry to prove identity: purity on its own only says a sample is clean, not that it is the compound you ordered.
- An identical CoA appearing on every order: a real one is made fresh for each batch.
- Net peptide content left off altogether: without it, the true amount is anyone's guess.
How to ask for one
Every batch we list carries its own traceable batch number and an HPLC and MS certificate of analysis, and it is yours on request. Have a look at quality & testing, or browse the catalogue.
Research use only. Everything mentioned here is supplied strictly as laboratory reference material for in-vitro research. It is not a medicine and is not meant for human or veterinary consumption, or for diagnostic or therapeutic use.
