HPLC is the analytical technique used to determine the purity of a peptide compound, expressed as the integrated chromatographic peak area relative to total area and reported as a percentage.
HPLC separates the components of a sample as they pass through a stationary phase under high pressure. A peptide produced by solid-phase peptide synthesis will, in practice, include trace amounts of truncated chains, deletion sequences, and protecting-group residues alongside the target compound.
HPLC quantifies how much of the sample is the target peptide vs. impurities. The result — a percentage of integrated peak area — is what appears on the Certificate of Analysis as the purity figure for a specific lot.
Every lot we ship is tested by a third-party laboratory. The purity number on each COA is the integrated HPLC area for that specific batch — not a marketing target. A supplier publishing a flat figure on every product is selling the label, not the assay.