Vetted Vial Editorial · Published / reviewed 2026-10-23
A peptide certificate of analysis is a report of specified tests on an identified sample. Start with the sample and method, then read the result. A high purity number alone cannot authenticate the document, establish the amount in every vial, or certify a supplier.
1. Match the identifiers before reading the numbers
Record the compound name, sequence or product identifier where provided, report number, sample ID, supplier lot number, laboratory, and test date. Compare the lot with the material you are investigating. Ask the issuer to explain missing or conflicting identifiers rather than guessing that two similar names describe the same material.
Keep the original PDF or public report URL and its revision date. A cropped screenshot can omit the method, units, conditions, or qualifications that explain the result.
2. Separate the questions each test answers
| Reported item | Question to ask the laboratory |
|---|---|
| Identity / mass spectrometry | What identity conclusion does the measured mass support, and what additional evidence is needed? |
| HPLC area purity | Which detected peaks are included, and what method and integration rules were used? |
| Content or assay | What amount was measured, in which units, using what calibration and reporting basis? |
| Other tests | Which additional measurements were actually performed on this sample? |
GenScript’s QC-report guide explains HPLC chromatograms and mass-spectrometry reports. HPLC separates components under specified conditions; the detector trace and integrated peak areas support the reported purity. Mass spectra show mass-to-charge signals that require interpretation. Ask for the laboratory’s acceptance criteria rather than applying a universal mass tolerance.
3. Ask for the supporting data
Request the chromatogram, peak table, relevant spectrum, method reference, and any interpretation notes. A summary certificate may not contain every supporting record. Missing graphs are a reason to ask what is available, not automatic evidence that a report is false.
Ask whether the method can distinguish likely related compounds and whether unresolved components or detector response affect interpretation. A matching mass alone need not distinguish all possible structures. Have the issuing laboratory explain any conclusion beyond the measurements shown.
4. Read quantity separately from purity
If your question is how much peptide is present, look for a content or assay result and its reporting basis. An area percentage is not a milligram value. Check whether a stated weight means gross powder, net peptide material, or a quantified target compound. Our purity and net-content guide explains the distinction with a fictional example.
5. Authenticate the report and its scope
Use contact details from the laboratory’s official website or its report-verification portal. Ask whether the report number, sample ID, results, and revision match its records. Confirm who submitted the sample and how the supplied lot identifier was recorded. Authenticity of a report does not prove that the sample represents every vial sold under a lot number.
If accreditation is claimed, check the named laboratory, site, and relevant test in its current scope. See questions to ask a testing laboratory for the practical checks.
Keep the uncertainties alongside the result
- Save the complete report and its source.
- Record unmatched identifiers and unanswered method questions.
- Distinguish a result from a specification or acceptance limit.
- Do not infer unreported tests or company-wide quality from one sample.
- Ask the laboratory to clarify corrections or amended reports.
A useful review of a COA explains what is known, what was measured, and what remains unanswered. Return to the company comparison checklist.
For laboratory research and business education only. A report or listing does not establish suitability for human use.
Sources checked October 23, 2026. Questions or corrections? Contact the editorial team.