Before reading the numbers
A certificate of analysis (CoA) records analytical findings for an identified sample or batch. Begin with the issuing laboratory, report identifier, sample description, lot number, and analysis date. The report should be traceable to the material in front of you.
A professional layout, logo, or QR code is not authentication. Where verification is needed, confirm the report with its issuer using independently established contact details.
The fields that deserve a closer look
| Field | What it means | Warning sign |
|---|---|---|
| Compound name | The declared identity, including sequence, modifications, and salt form where relevant. | An ambiguous abbreviation or a name that does not match the container. |
| Lot / batch number | The link between the tested sample, the report, and a specific material batch. | A missing identifier, a mismatch, or one generic report used for unrelated lots. |
| HPLC purity | Usually a relative chromatographic peak-area percentage under the stated method. It is not the mass fraction of peptide in the vial. | A percentage without a method or chromatogram, or an assumption that it measures every impurity. |
| Mass / amount | Molecular mass characterizes the molecule; gross vial mass and net peptide content describe different quantities. Check units and method. | Molecular mass confused with vial content, or a stated amount without a clear measurement basis. |
| Analytical method | The technique and conditions behind the result. HPLC and mass spectrometry answer different analytical questions. | Only “pass” reported, no identifiable method, or a result that does not support the claimed characteristic. |
| Storage conditions | The stated conditions for the documented material form, with any relevant retest or expiry date. | Missing conditions, conflicting documents, or dry-material instructions applied to a solution. |
What a CoA does not establish
Identity, purity, and quantity are different questions. A dominant HPLC peak does not by itself identify a compound, and a matching molecular mass alone does not establish the complete sequence. These distinctions are discussed in the published peptide characterization guidance.
A CoA describes the scope of the tests reported. Do not infer sterility, absence of all contaminants, long-term stability, or regulatory authorization from an unrelated analytical result.
When information is missing
Record the discrepancy and ask the issuing laboratory for clarification or supporting records. Keep the material outside the relevant laboratory workflow until the responsible person has resolved the issue under the institution’s procedures.
A clear report distinguishes a measured result from a specification limit and identifies any qualification or uncertainty relevant to interpretation.
Sources & further reading
MilliporeSigma · Peptide synthesis and analytical quality control