How to Read a Research Peptide COA: HPLC Purity, Mass Spec and What's Missing

A Certificate of Analysis is the only evidence a research buyer has that a peptide batch is what it claims to be. Reading it well means knowing which tests matter for peptides — and which ones are often missing.

Identity: mass spectrometry

Mass spectrometry confirms the molecular weight. The COA should show the observed mass next to the theoretical mass for the sequence (often as the [M+H]+ ion) and state that they agree within tolerance. Mass alone does not prove sequence order; for critical work ask for peptide mapping or sequencing.

Purity: HPLC

Reverse-phase HPLC reports the percentage of the chromatogram that is the target peptide. A useful COA states the column, mobile phase, detection wavelength and integration, or includes the chromatogram. Red Chem Biotech supplies peptides at a minimum of 99.0% by HPLC.

Peptide content and counter-ion

HPLC purity is not the amount of peptide in the powder. Lyophilised peptides contain water and counter-ions such as acetate or trifluoroacetate (TFA). Net peptide content — by amino acid analysis or nitrogen determination — tells you how much of the weight is actually peptide, which matters for any quantitative work.

Tests HPLC and MS do not cover

• Water content (Karl Fischer)
• Counter-ion content (acetate or TFA)
• Bacterial endotoxins, where the application requires it
• Residual solvents and appearance of the lyophilised cake

Red flags on a peptide COA

• No batch number, or a batch number that does not match the label
• Purity without a method or chromatogram
• No mass result, or a mass that does not match the sequence
• "Typical" values instead of batch results
• No date or authorisation

Research use only

Research peptides are supplied for in-vitro and laboratory research. They are not medicines and are not for human or veterinary use. Every Red Chem Biotech peptide ships with its batch COA and Safety Data Sheet.