Pure Peptides UK: What Purity Claims Really Mean

"Purity" is three different questions

When a supplier says a peptide is pure, check that all three of these are answered:

1. Is it the right molecule? That is identity, confirmed by mass spectrometry.
2. How much of the sample is that molecule? That is purity, measured by HPLC.
3. How much peptide is actually in the vial? That is net peptide content. It is affected by counter-ions such as acetate or TFA, and by water.

A high HPLC figure on its own answers only the second question.

What good documentation looks like

• A batch or lot number that matches the product you'll receive
• A recent test date
• An HPLC chromatogram, not just a percentage
• Mass-spec data showing the observed mass matches the expected molecular weight
• The testing laboratory named, ideally an independent third party

Our step-by-step guide covers each of these in more depth: how to read a peptide certificate of analysis.

Red flags

• The same certificate reused across many batches or products
• Purity quoted with no chromatogram
• No mass-spec data
• A laboratory that can't be identified or contacted

How PeptideCompare shows documentation

Each listing shows whether the supplier has uploaded a certificate of analysis, and supplier pages show what suppliers say about third-party testing. Unless a listing is marked as staff-verified, these documents are supplier-provided and not independently verified by PeptideCompare. Documentation also feeds into each supplier's confidence score.

Storage affects purity too

A peptide that was pure when tested can degrade through heat, moisture or repeated freeze–thaw cycles. See how research peptides are stored and handled.

Research use only

All listed products are third-party materials for in-vitro laboratory research. They are not for human or veterinary use, and we give no dosing guidance.

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