How to read a Certificate of Analysis
Understanding HPLC purity, mass-spec identity, and lot verification
A Certificate of Analysis (COA) is the lab document that tells you what is actually in a vial. For research peptides it is the single most important quality signal — here is how to read one.
HPLC purity
High-Performance Liquid Chromatography separates the contents of a sample and measures each component as a peak. The purity percentage is the target peptide's share of the total — a ≥99% result means the overwhelming majority of the material is the intended peptide with minimal related impurities. The chromatogram (the trace of peaks) should show one dominant peak.
Mass-spectrometry identity
Mass spectrometry confirms identity by measuring the peptide's molecular mass. The measured mass should match the theoretical mass for that sequence — this is how you know the vial contains the peptide it claims to, not merely a pure something-else.
Lot number & traceability
A COA is tied to a specific lot. The lot on your vial should match the lot on the certificate and its test date. That linkage is what makes a COA meaningful rather than generic marketing.
Verify any Glow Peptides lot
Every lot we ship is independently tested at a U.S. laboratory and carries its own COA. You can search a lot and view its purity and test date on our Quality & COA verification page — no purchase required.
Frequently asked questions
What purity should a research peptide be?
Higher is better; our standard is ≥99% by HPLC. The COA states the exact figure for that specific lot.
What does "independent U.S. lab-tested" mean here?
Testing is performed by an independent United States laboratory rather than only in-house, using HPLC-UV for purity and mass spectrometry for identity, on a per-lot basis.
Can I see a COA before buying?
Yes. Our Quality & COA verification page lets you search a lot and view its documentation without a purchase.