Quality education · 4 min read
What "99% Purity" Really Means on a Research Peptide
HPLC purity, identity and net content are three different measurements. Here is how to tell whether a purity claim is backed by data.
"99% purity" is the most common claim in the research peptide market and one of the least understood. It refers to one specific measurement and leaves out several others.
What it does measure
HPLC purity is the share of UV-absorbing material in the sample that elutes as the target peak. It is a measure of how much of the peptide-like material is the intended sequence rather than truncated or modified synthesis by-products.
What it does not measure
- Identity. Only mass spectrometry confirms the peak is the right molecule.
- Net content. Counterions and water do not show up as impurities on a UV chromatogram, yet they can be a quarter of the vial's mass.
- Endotoxin. Bacterial endotoxin is measured separately (USP <85>, LAL or rFC methods) and reported in EU/mg.
A quick credibility test
Ask for three things: the chromatogram with its detector wavelength, the observed versus theoretical mass, and the lot number that ties both to the vial. Suppliers priced far below market rarely provide all three, because the testing has a real cost.
Every Atlas lot links its full report from the product page and the COA library.
Keep reading
- How to Read a Peptide Certificate of Analysis
- Net Peptide Content vs Gross Weight: What a "10 mg" Vial Contains
Research use only. For Research Use Only. Not for human or veterinary use. Not for diagnostic or therapeutic use. Not a drug, food, cosmetic or dietary supplement. Not for resale to consumers.
