A Certificate of Analysis is a technical document, not a marketing badge. The headline purity number is the least interesting part of it: the chromatogram beneath that number tells you where the impurities are and whether they are structurally related to your target sequence.
Start with the HPLC trace. A single sharp main peak with a clean baseline indicates a well-purified product. Shoulders adjacent to the main peak usually indicate deletion or truncated sequences, which are the hardest impurities to remove and the most likely to interfere with binding studies.
Move to mass spectrometry. The observed mass should match the theoretical monoisotopic mass of the sequence within a fraction of a Dalton. A systematic offset can indicate incomplete deprotection or an oxidised residue.
Finally, check endotoxin and heavy metals. Endotoxin is reported in EU/mg and matters enormously for any cell-based work: contamination here produces inflammatory artefacts that look like real signal. Heavy-metal screening catches catalyst and reagent carryover from synthesis.
If a supplier cannot produce a lot-specific COA with all four sections, treat the material as uncharacterised, regardless of what the label claims.
For laboratory research use only. This article is general information and is not medical advice.
