What 99% Purity Actually Means on a Peptide COA
Nearly every vendor advertises purity above 99%. The figure is meaningful, but narrower than most buyers assume, and the gap is the difference between reading a certificate and trusting a slogan.
What the number measures
Purity on a peptide COA is almost always an HPLC peak-area percentage: the sample is separated on a column, components detected by UV absorbance at 220 nm where the peptide bond absorbs, and the main peak expressed as a fraction of total peak area.
What it does not measure
Not identity. Peak area says one component dominates; it does not say that component is the molecule on the label. Only mass spectrometry — observed against theoretical mass — confirms identity. A COA with purity but no MS is incomplete.
Not mass of peptide in the vial. Peptides are supplied as salts, commonly trifluoroacetate or acetate, and lyophilized material retains water. Counter-ion and water content account for a real share of vial weight. Peptide content assays address this; peak-area purity does not.
Only what the detector sees. UV at 220 nm detects peptide bonds. Substances that do not absorb there — many salts and residual solvents — are invisible to the measurement.
Reading a certificate properly
Check the lot number on the report matches the vial in your hand; a generic COA proves nothing about your batch. Look for the chromatogram itself, not only the summary figure. Confirm mass spectrometry is present and matches. Note who performed the analysis — a third-party lab has no stake in the result.
Why per-lot reports matter
A purity claim that cannot be traced to a batch is marketing. Every VitaPep lot is batch-stamped and its report retrievable by lot number on our certificates page.
EDUCATIONAL CONTENT ON PUBLISHED RESEARCH · ALL VITAPEP PRODUCTS ARE FOR LABORATORY RESEARCH USE ONLY AND NOT FOR HUMAN OR VETERINARY USE.
EDUCATIONAL CONTENT ON PUBLISHED RESEARCH · ALL VITAPEP PRODUCTS ARE FOR LABORATORY RESEARCH USE ONLY AND NOT FOR HUMAN OR VETERINARY USE.