Most peptide certificates of analysis lean on two techniques: HPLC-UV and LC-MS. They are often mentioned together, but they answer two different questions — and a trustworthy COA needs both.
HPLC-UV answers: how much?
High-performance liquid chromatography separates the contents of a sample as they pass through a column, and a UV detector measures each component as it comes out. The result is a chromatogram — a series of peaks — where the main peak’s share of the total area is the purity percentage. When a COA says 99.4% purity by HPLC-UV, it means 99.4% of the UV-detectable material was one compound.
LC-MS answers: is it the right molecule?
Mass spectrometry weighs the molecules themselves. Every peptide has a precise molecular mass determined by its sequence, so a matching mass is strong evidence the compound is what the label claims. This is the identity check — purity alone cannot prove identity, because a sample can be 99% pure and still be 99% of the wrong compound.
Why you should insist on both
A COA showing only purity leaves the identity question open; one showing only identity says nothing about contamination. Reading them together: LC-MS confirms the molecule, HPLC-UV quantifies how clean it is. Anything else on the certificate — appearance, accession number, test dates — supports traceability.
Check a real one
Every ANKR Lab lot is tested for both by an independent laboratory, and every certificate is public. Pick any lot in the COA library and open the PDF — you will find the HPLC-UV purity result and the LC-MS identity confirmation on the same report. For the full pipeline from quarantine to release, see how we test, and for a field-by-field walkthrough, our guide on how to read a peptide COA.
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