Reading a Certificate of Analysis

A Certificate of Analysis is the primary document linking a research peptide to its identity, purity, and quality attributes. Reading one fluently is a basic skill for anyone procuring research materials.

Identity confirmation

Mass spectrometry (typically MALDI-TOF or ESI) confirms the peptide's molecular weight matches the theoretical value within instrument tolerance, usually ±1 Da.

Purity by HPLC

Look for the chromatogram itself — not just the printed percentage. A sharp, symmetric main peak with minimal shouldering indicates a clean synthesis. Broad or split peaks may suggest sequence isomers.

Counter-ion content

Net peptide content is often lower than total mass once acetate or TFA counter-ions and residual water are subtracted. For dose calculations, use net peptide content, not gross weight.