Understanding the certificate of analysis and what purity actually means
Innovatix Admin · Apr 17, 2026 · 1 min read
Decoding HPLC chromatograms, mass-spec confirmations, and the difference between peptide content and gross weight.
The certificate of analysis (CoA) is the document that turns a vial of white powder into a known reagent. Reading one well takes a few minutes and saves hours of troubleshooting later.
HPLC purity
The headline number on most CoAs. A high-performance liquid chromatography trace at 220nm shows the absorbance peaks of every UV-active compound in the sample. Integration gives a percentage; 99%+ is the bar for sensitive assays.
Mass spectrometry
Confirms the molecular weight matches the claimed sequence. Without MS confirmation, HPLC purity tells you the sample is clean — not that it's the right thing.
Peptide content vs. gross weight
Lyophilized peptide salts include counterions (TFA, acetate). A vial labelled "10 mg" might be 8.7 mg of net peptide and 1.3 mg of TFA. For dose calculations, peptide content matters; for handling, gross weight does.