High-performance liquid chromatography (HPLC) separates the components of a sample so they can be measured individually. On a peptide COA it is the primary evidence of purity.
Reading the chromatogram
The horizontal axis is time; the vertical axis is detector response. Each peak represents a compound eluting from the column at a characteristic time. The large, dominant peak is your target peptide.
The main-peak percentage
Purity is reported as the area of the main peak divided by the total area of all peaks. A figure such as 98–99% means the overwhelming majority of the material is the target compound.
Look beyond the headline number
- Number of impurity peaks — a few tiny peaks differ from many moderate ones.
- Peak shape — sharp, symmetrical peaks suggest a clean separation.
- Baseline — a flat, stable baseline indicates a well-run method.
Pair it with identity
HPLC tells you how pure the material is; it does not by itself confirm what the material is. That is why a complete COA pairs HPLC purity with mass spectrometry identity.
Research use only.