Read a peptide COA as a set of separate, method-specific results. First match the report to the material; then distinguish identity, chromatographic purity and content rather than treating one percentage as a complete quality verdict.
Match the document before reading the number
Compare the product name and lot or batch identifier on the report and on the vial. Review the sample description, report date and laboratory. Missing or conflicting identifiers weaken the connection between the report and the material in hand.
Separate the analytical questions
| Identity | Mass spectrometry may compare an observed mass with the expected mass. |
|---|---|
| HPLC purity | A peak-area percentage under the stated chromatographic method; it is not the same as total peptide content. |
| Content | The peptide mass fraction can differ from an HPLC area result because water, salts and counter-ions may contribute to sample mass. |
| Sterility and endotoxin | Separate questions requiring their own methods; neither follows from an HPLC purity result. |
Ask what the report actually supports
Check whether the method, result, units and acceptance criteria are visible. Do not infer fill quantity, sterility, biological activity or suitability from an identity or purity line. Technical suppliers and pharmacopeial resources describe these as distinct quality attributes. [GenScript peptide purity guidance][USP peptide quality resources]
Check presentation and context
A graph without a readable sample identifier or method conditions offers limited context. Note whether chromatograms and spectra are attached, whether axes and peaks are legible, and whether the stated conclusion clearly corresponds to those pages. This is a document-consistency check, not an independent validation of the laboratory work.