Every credible peptide Certificate of Analysis leans on two tests: HPLC and mass spectrometry. They sound technical, but the idea behind each is simple — and understanding them is the difference between reading a CoA and just glancing at it. Here's what each one actually measures.
HPLC: how pure is it?
HPLC stands for high-performance liquid chromatography (you'll often see RP-HPLC — the "RP" is reverse-phase). In plain terms, it separates everything in the sample into its individual components and measures how much of each is present. The result is your purity percentage — for example, 99.5%. That number tells you how much of the sample is the target compound versus impurities or by-products.
A tall, clean single peak on the chromatogram means the sample is overwhelmingly one substance. Smaller extra peaks are impurities. So HPLC answers one question: how clean is it?
Mass spectrometry: is it the right molecule?
Mass spec (often written LC-MS) measures the molecular weight of the compound and compares it to the known weight of the target peptide. If they match, the sample's identity is confirmed — it really is the peptide it claims to be.
This is the question HPLC can't answer. HPLC tells you the sample is clean; it doesn't tell you it's the right clean compound. Mass spec does. That's why both appear on a proper CoA.
Why purity and identity are two different questions
This is the single most important thing to understand:
- High purity, no identity test = "this is 99% of something" — but you don't know what.
- Identity confirmed, no purity test = "it's the right molecule" — but you don't know how much filler is in there.
- Both = you know it's the right compound and that it's clean. This is what you want.
A supplier showing only a purity number is answering half the question. Look for both HPLC purity and mass-spec (or LC-MS) identity confirmation.
How to check it's genuine
The strongest certificates come from an independent third-party lab and carry a report number plus a verification code you can confirm on the lab's own website. If a CoA has no batch number, no named lab, no method stated, or no way to verify — treat it with caution. Our full guide on how to read a Certificate of Analysis walks through every section.
See real results
Every batch we distribute is tested for both — RP-HPLC purity and LC-MS identity — and the certificates are published openly. Have a look at the actual chromatograms and results in our CoA Library to see exactly what complete testing looks like.
All products are supplied strictly for laboratory and in-vitro research use only. Not for human or veterinary consumption. This article is general information about laboratory analysis and is not medical advice.