Mass Spectrometry for Peptide Identity
How mass spec confirms peptide identity and molecular mass — and why it pairs with HPLC purity in a Certificate of Analysis.
Why identity matters separately from purity
A chromatogram can show a single sharp peak, indicating a highly pure sample, while still containing the wrong compound. Mass spectrometry confirms that the molecule eluting from the HPLC column matches the expected peptide's molecular mass.
What appears on a COA
- Theoretical monoisotopic or average mass of the peptide.
- Measured mass from the mass spectrometer.
- Mass-deviation tolerance (often in parts-per-million for high-resolution instruments).
HPLC + mass spec together
Used together, the two methods answer the two questions a researcher cares about: is the sample mostly one thing (HPLC purity), and is that thing actually the peptide on the label (mass spec identity).