HPLC purity, LC-MS identity and peptide content

Three questions, not one score

Research peptide documentation should distinguish what was separated, what was identified and what was quantified. A standalone “purity” number does not answer all three questions.

High-performance liquid chromatography (HPLC) separates components under a particular method’s conditions. An area percentage describes the signals integrated within that method. It should not automatically be read as the mass fraction of everything inside a vial.

What does mass spectrometry add?

Mass spectrometry and, where applicable, fragmentation can provide complementary identity information. NIST distinguishes such qualitative information from methods used to assign concentration. The label “LC-MS” does not replace reading the actual result and acceptance criteria.

Approaches investigated for peptide content include mass balance, amino acid analysis and quantitative NMR. Interpretation depends on the procedure, references and impurities accounted for.

A practical documentation request

Ask for the chromatogram and relevant conditions, sample identification, the identity method, and the exact unit used for any measured content. Record unreported analyses separately. A confirmed identity is not a guarantee that every contaminant is absent, nor does it authorize human use.

These points concern laboratory documentation, not product preparation or administration.

Sources and next steps

• NIST: amino acid analysis and qualitative identity information
• NIST: peptide purity mass-fraction assignment
• Read a peptide COA
• Catalog and analysis status by reference