HPLC purity: what "≥97%" on a certificate of analysis actually tells you

A reported HPLC purity of ≥97% means 97% of the UV-absorbing material at the assay wavelength is the target peptide. The remaining 3% is typically a mixture of truncation sequences, deletion sequences, and racemisation byproducts — impurities that share enough structural similarity to the target that they were not removed during preparative purification.

What HPLC purity does not tell you: net peptide content (which requires amino acid analysis or nitrogen determination), counter-ion content (typically TFA or acetate), or residual solvent load. A vial labelled "5 mg BPC-157, ≥97% HPLC" may deliver noticeably less than 5 mg of net peptide once water, counter-ion, and impurities are accounted for.

Our HPLC & COA guide walks through every line item on a typical certificate.