Short answer
A useful peptide COA should connect one identifiable batch to reproducible analytical evidence. Check the sample or batch identifier first, then separate identity evidence from purity and content measurements. Confirm the laboratory, test date, analytical methods, numerical results, and any public verification key.
A purity percentage alone does not establish molecular identity or the amount of peptide in a vial.
Key facts
- Identity, purity, and content answer different questions and should not be treated as interchangeable.
- The batch or sample identifier on the report should match the material being supplied.
- A public verification key is useful only when the laboratory record matches the unedited report.
- Method details and system suitability provide context for whether a result is fit for its stated purpose.
- A COA is one part of supplier qualification, not a substitute for traceability and receiving controls.
Start with report identity and traceability
Record the issuing laboratory, task or report number, client or manufacturer name, sample name, batch identifier, testing dates, and verification key. These fields establish what was tested and when. If the supplied vial uses a different batch code, the report may still describe the same compound but it does not provide batch-specific evidence for that vial.
Preserve the original report because changing client, manufacturer, QR code, signature, result, or verification text can break the connection to the laboratory record.
Separate identity, purity, and content
Identity testing asks whether the principal analyte is consistent with the expected molecule. Mass spectrometry is commonly used to compare an observed ion pattern or deconvoluted mass with an expected molecular mass. Chromatographic purity estimates the relative signal assigned to the principal peak under stated conditions.
Content or quantity testing estimates how much target material is present. A report can show high chromatographic purity while measured content differs from a label claim, so laboratories should review each result independently.
Read the HPLC result in context
Do not stop at the printed purity percentage. Review the chromatogram, detector type and wavelength when available, column and mobile-phase information, run time, retention time, integration, principal peak, and visible secondary peaks.
Area normalization is method-dependent: it compares integrated detector responses and may not account for substances that do not respond at the selected wavelength. The method should be suitable for the analyte and the report's intended claim.
Review mass-spectrometry evidence
Check whether the report gives the expected molecular formula or mass, observed ions, charge states, adducts, and a calculated or deconvoluted mass. Peptides commonly produce multiple charge states, so a raw mass-to-charge value is not automatically the intact molecular mass.
The observed result should be explained by the expected molecule, ionization mode, salt form, counterions, and stated method.
Use a repeatable acceptance checklist
A receiving laboratory can document five decisions: the report is authentic, the material and report are traceably linked, the methods are appropriate, the results meet internal specifications, and any discrepancy has been resolved before release.
Keep the report, verification evidence, purchase record, received batch photographs, and internal disposition together. This creates a reviewable chain from supplier claim to laboratory acceptance.
Frequently asked questions
Does 99% HPLC purity mean the vial contains 99% of the labeled amount?
No. HPLC area purity and measured vial content are different measurements. A separate quantitative assay or content test is needed to evaluate the amount present.
Can a supplier rename the client on a third-party COA after rebranding?
The original laboratory report should remain unedited. A supplier can add a separate rebranding note, but an amended client or manufacturer field should come from the issuing laboratory.
Is one analytical technique enough for peptide verification?
It depends on the claim and method, but orthogonal evidence is stronger. Chromatography can support purity assessment while mass spectrometry can support molecular identity.