Three methods, three questions
Analytical characterization answers three separate questions about a peptide batch. No single measurement answers all three, which is why a complete certificate reports them together.
- HPLC — how pure is it? (area percentage of the target peak).
- Mass spectrometry — what is its molecular weight? (identity confirmation).
- Amino acid analysis — what is its composition and content?
HPLC: purity
Reversed-phase HPLC separates the components of a sample by hydrophobicity and reports the target peak as a percentage of total area. A purity of 98% or higher is typical for research-grade peptides, but the number is only meaningful alongside the method that produced it.
Mass spectrometry: identity
Mass spectrometry measures the mass-to-charge ratio of ionized molecules, confirming that the material has the expected molecular weight. A purity figure cannot catch a sequence error or a salt mismatch — mass spectrometry can.
Amino acid analysis: composition and content
Amino acid analysis hydrolyzes the peptide and quantifies the released residues, confirming composition and reporting peptide content separately from gross vial fill. This is the measurement that ties a stated mass to actual active material.
Why one number is not enough
A single purity percentage does not confirm identity, nor does it tell you how much active peptide is in the vial. A documented batch reports purity, identity, and content together so each can be checked independently.