HPLC
High-performance liquid chromatography — the principal method for assessing peptide purity.
For laboratory and research use only — not for human consumption.
HPLC separates molecules based on differential affinity for a stationary phase as they elute through a packed column under high pressure. For peptides, reversed-phase HPLC with C18 columns and acetonitrile-water-trifluoroacetic-acid gradients is the standard format. Purity is reported as the percentage of total UV peak area at 220 nm (peptide bond absorbance) or 280 nm (aromatic residue absorbance). Research-grade injectable peptides typically require ≥ 98% HPLC purity; lower purity batches are acceptable for some in-vitro work but should be evaluated carefully.