How to Read a Peptide Certificate of Analysis
Every reputable peptide supplier publishes certificates of analysis (COAs), but a report is only useful if you know how to read it. This guide walks through the sections of a typical COA and the specific things worth checking before you trust a purity claim — ours or anyone else’s.
1. The identity block
The top of the report should identify the compound, the lot number, the synthesis and analysis dates, and — critically — the laboratory that performed the testing. A COA generated by the seller’s own in-house lab is not worthless, but an independent third-party report is a meaningfully stronger signal, because the tester has no stake in the result. Check that the lot number on the report matches the one printed on your vial: a generic COA with no lot number tells you nothing about the batch you actually received.
2. HPLC purity — what the percentage means
High-performance liquid chromatography separates the contents of a sample as they pass through a column; each component appears as a peak on the chromatogram, and detection is typically by UV absorbance at 220 nm, where peptide bonds absorb. The purity figure — say, 99.4% — is the area of the main peak as a percentage of the total peak area. Two things to inspect:
- The chromatogram itself. A trustworthy report includes the full trace, not just a number. A clean profile shows one dominant peak with only minor secondary peaks. If the trace is missing, ask why.
- The retention time. The main peak should elute at a retention time consistent with the compound and method. This is what ties the purity number to the right substance.
3. Mass spectrometry — the identity check
Purity alone doesn’t prove identity: a sample can be 99% pure and still be 99% of the wrong molecule. Mass spectrometry closes that gap by measuring the molecular mass of the main component. The report should state the theoretical (calculated) mass of the peptide and the observed mass; the two should agree within the instrument’s tolerance. A COA with HPLC purity but no mass confirmation is an incomplete report.
4. What a good report will admit
Honest analytical reporting includes the things marketing wouldn’t: the counter-ion content (peptides are commonly supplied as trifluoroacetate or acetate salts, which contributes to vial mass), water content from lyophilization, and the method parameters used. Vagueness in these sections is a mild warning sign; their presence is a good one.
Checking a VitaPep lot
Every VitaPep vial is batch-stamped, and the third-party report for each released lot — chromatogram, retention data, and observed mass included — is available through our COA lookup page. If a report ever fails to match its label claim, our terms provide for replacement or refund.
All VitaPep products are supplied strictly for laboratory research use and are not for human or veterinary use.
All compounds supplied by VitaPep are for in-vitro laboratory research use only. Nothing on this page is guidance for human or veterinary use of any kind.
EDUCATIONAL CONTENT ON PUBLISHED RESEARCH · ALL VITAPEP PRODUCTS ARE FOR LABORATORY RESEARCH USE ONLY AND NOT FOR HUMAN OR VETERINARY USE.