What is HPLC? (Peptide Glossary)

HPLC separates the components of a sample by passing it through a packed column under high pressure. Different molecules travel through the column at different speeds, so the target peptide emerges at a characteristic time (retention time) and appears as a peak on the chromatogram. The area of that peak relative to all peaks gives the purity percentage.

When a COA states 98.5% purity by HPLC, it means 98.5% of the detected material was the target peptide and 1.5% was impurities - typically deletion sequences (chains missing an amino acid), truncated fragments, or residual solvents from synthesis. For research peptides, 98% or higher is the accepted quality threshold; 95-98% is marginal; below 95% should not be sold.

A real HPLC result includes the chromatogram itself - a graph showing the peaks. This matters because a bare percentage can be invented, while a chromatogram shows the actual data. When reviewing a COA, look for a single dominant peak, the testing date, the column and method details, and the lab identification. Vendors who publish full chromatograms per batch are demonstrating real quality control.