The phrase "≥99% purity" appears on nearly every research peptide listing — yet the number alone conveys little about analytical rigor. This article explains how meaningful purity standards are established and what researchers should demand from suppliers.
Defining purity analytically
Purity is not a single universal constant. It is the area percent of the target sequence integrated under a defined HPLC method. Change the column, gradient, or wavelength and the reported value shifts. Credible suppliers publish method summaries alongside COAs.
For a typical synthetic peptide such as BPC-157, the molecular formula C62H98N16O22 reflects the target sequence; impurities include N-terminal deletions, incomplete coupling products, and disulfide misfolds in cysteine-rich sequences.
Industry benchmark tiers
When purity is not enough
Aggregation, even at sub-percent levels, can dominate biological activity. Dynamic light scattering and SEC-HPLC are complementary tests we perform on select catalog items and upon request. Ask for oligomer data when your assay is sensitive to multimeric state.
Transparency beats headline numbers. Request raw chromatogram PDFs, integration parameters, and reference standard lot traceability — a supplier willing to share is a supplier worth trusting.